Laminated glass intermediate film and laminated glass

ABSTRACT

The present invention provides an intermediate film for laminated glass which can improve sound insulation. The intermediate film has a layered structure including at least two layers, comprising: a first layer containing a polyvinyl acetal resin and a plasticizer; and a second layer positioned on a first surface of the first layer. In a phase diagram of three values including a degree of acetalization, a degree of acetylation, and a hydroxyl group content of the polyvinyl acetal resin contained in the first layer, the values of the degree of acetalization, the degree of acetylation, and the hydroxyl group content each fall within a region surrounded by a line including four straight lines connecting first, second, third, and fourth coordinates, which respectively have a degree of acetalization:degree of acetylation:hydroxyl group content of 70 mol %:30 mol %:0 mol %, 34 mol %:30 mol %:36 mol %, 94 mol %:0 mol %:6 mol %, and 100 mol %:0 mol %:0 mol %.

TECHNICAL FIELD

The present invention relates to an intermediate film for laminatedglass used in laminated glass for automobiles, buildings and the like.More specifically, the present invention relates to an intermediate filmfor laminated glass which contains a polyvinyl acetal resin and aplasticizer, and a laminated glass using the intermediate film forlaminated glass.

BACKGROUND ART

Laminated glasses scatter fewer pieces of broken glass when they aredamaged by external impact, and thus are excellently safe. Therefore,such laminated glasses are widely used in automobiles, railwaycarriages, aircrafts, ships, buildings, and the like. The laminatedglass is produced by interposing an intermediate film between a pair ofglass plates.

In order to reduce the weight of a laminated glass, studies haverecently been performed for making a laminated glass thin. A thinnerlaminated glass, however, has a reduced sound-insulating property. If alaminated glass with a reduced sound-insulating property is used for thewindshield of an automobile, its sound-insulating property isdisadvantageously insufficient against sounds at a register of about5,000 Hz, such as wind noise and driving sound of wipers.

Then, additional studies have been performed for increasing thesound-insulating property of a laminated glass by changing materials ofan intermediate film.

Patent Document 1 discloses, as one example of an intermediate film forlaminated glass, a sound-insulating layer including 100 parts by weightof a polyvinyl acetal resin with a degree of acetalization of 60 to 85mol %, 0.001 to 1.0 parts by weight of at least one metal salt selectedfrom alkali metal salts and alkaline earth metal salts, and 30 parts byweight or more of a plasticizer. This sound-insulating layer can be usedalone as an intermediate film, or can be laminated with another layerand used as a multilayer intermediate film.

RELATED ART DOCUMENT Patent Document

-   Patent Document 1: JP 2007-070200 A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In the case of a laminated glass including the intermediate filmdisclosed in Patent Document 1, the sound-insulating property isincreased to some extent. However, the sound-insulating property isstill needed to be increased.

In the case of forming a laminated glass using the intermediate filmdisclosed in Patent Document 1, the sound-insulating property of thelaminated glass in a relatively high frequency range is insufficient,and thus reduction in the sound-insulating property due to thecoincidence effect cannot be avoided in some cases. In particular, thesound-insulating property of the laminated glass at around 20° C. may beinsufficient.

Here, the coincidence effect is a phenomenon that, when sound wavesstrike a glass plate, the transverse wave is propagated on the glasssurface due to the rigidity and inertia of the glass plate, and then thetransverse wave resonates with the incident sound, so that the sound istransmitted.

Further, in the case of forming a laminated glass using a multilayerintermediate film disclosed in Patent Document 1 in which thesound-insulating layer and other layers are laminated, thesound-insulating property of the laminated glass at around 20° C. can beimproved to some extent. In this case, however, the multilayerintermediate film has the sound-insulating layer, and thus bubbleformation may occur in the laminated glass including the multilayerintermediate film.

Furthermore, recently, it has been studied to increase the amount of aplasticizer contained in an intermediate film in order to improve thesound-insulating property of a laminated glass. As the amount of aplasticizer in an intermediate film increases, the sound-insulatingproperty of the laminated glass can be improved. If the amount of aplasticizer increases, however, bubble formation may occur in thelaminated glass.

An object of the present invention is to provide an intermediate filmfor laminated glass which can improve the sound-insulating property whenused in a laminated glass, and a laminated glass comprising theintermediate film for laminated glass.

A limitative object of the present invention is to provide anintermediate film for laminated glass which can provide a laminatedglass that not only has a high sound-insulating property but alsosuppresses bubble formation and bubble growth, and a laminated glasscomprising the intermediate film for laminated glass.

Means for Solving the Problems

According to a broad aspect of the present invention, provided is anintermediate film for laminated glass having a layered structureincluding at least two layers, including: a first layer containing apolyvinyl acetal resin and a plasticizer; and a second layer positionedon a first surface of the first layer, wherein, in a phase diagram ofthree values including a degree of acetalization, a degree ofacetylation, and a hydroxy group content of the polyvinyl acetal resincontained in the first layer, the values of the degree of acetalization,the degree of acetylation, and the hydroxy group content each fallwithin a region surrounded by a line including four straight linesconnecting a first coordinate (degree of acetalization:degree ofacetylation:hydroxy group content=70 mol %:30 mol %:0 mol %), a secondcoordinate (degree of acetalization:degree of acetylation:hydroxy groupcontent=34 mol %:30 mol %:36 mol %), a third coordinate (degree ofacetalization:degree of acetylation:hydroxy group content=94 mol %:0 mol%:6 mol %), and a fourth coordinate (degree of acetalization:degree ofacetylation:hydroxy group content=100 mol %:0 mol %:0 mol %) in thestated order.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, in the phase diagram of three valuesincluding a degree of acetalization, a degree of acetylation, and ahydroxy group content of the polyvinyl acetal resin contained in thefirst layer, the values of the degree of acetalization, the degree ofacetylation, and the hydroxy group content each fall within a regionsurrounded by a line including four straight lines connecting the firstcoordinate (degree of acetalization:degree of acetylation:hydroxy groupcontent=70 mol %:30 mol %:0 mol %), the second coordinate (degree ofacetalization:degree of acetylation:hydroxy group content=34 mol %:30mol %:36 mol %), a fifth coordinate (degree of acetalization:degree ofacetylation:hydroxy group content=95 mol %:0 mol %:5 mol %), and thefourth coordinate (degree of acetalization:degree of acetylation:hydroxygroup content=100 mol %:0 mol %:0 mol %) in the stated order.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, in the phase diagram of three valuesincluding a degree of acetalization, a degree of acetylation, and ahydroxy group content of the polyvinyl acetal resin contained in thefirst layer, the values of the degree of acetalization, the degree ofacetylation, and the hydroxy group content each fall within a regionsurrounded by a line including four straight lines connecting the firstcoordinate (degree of acetalization:degree of acetylation:hydroxy groupcontent=70 mol %:30 mol %:0 mol %), the second coordinate (degree ofacetalization:degree of acetylation:hydroxy group content=34 mol %:30mol %:36 mol %), the third coordinate (degree of acetalization:degree ofacetylation:hydroxy group content=94 mol %:0 mol %:6 mol %), and a sixthcoordinate (degree of acetalization:degree of acetylation:hydroxy groupcontent=95 mol %:5 mol %:0 mol %) in the stated order.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, in the phase diagram of three valuesincluding a degree of acetalization, a degree of acetylation, and ahydroxy group content of the polyvinyl acetal resin contained in thefirst layer, the values of the degree of acetalization, the degree ofacetylation, and the hydroxy group content each fall within a regionsurrounded by a line including four straight lines connecting the firstcoordinate (degree of acetalization:degree of acetylation:hydroxy groupcontent=70 mol %:30 mol %:0 mol %), the second coordinate (degree ofacetalization:degree of acetylation:hydroxy group content=34 mol %:30mol %:36 mol %), a fifth coordinate (degree of acetalization:degree ofacetylation:hydroxy group content=95 mol %:0 mol %:5 mol %), and a sixthcoordinate (degree of acetalization:degree of acetylation:hydroxy groupcontent=95 mol %:5 mol %:0 mol %) in the stated order.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, a peak temperature of tan δ whichappears at the lowest temperature measured at a frequency of 1 Hz is 0°C. or lower.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, a maximum value of tan δ at a peaktemperature of tan δ measured at a frequency of 1 Hz which appears atthe lowest temperature is 1.15 or more.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, the second layer contains a polyvinylacetal resin, and a carbon number of the acetal group of the polyvinylacetal resin contained in the second layer is 3 or 4, a degree ofacetalization thereof is not less than 60 mol % but not more than 75 mol%, and a degree of acetylation thereof is 10 mol % or less.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, the second layer contains a polyvinylacetal resin and a plasticizer, and the amount of the plasticizer for100 parts by weight of the polyvinyl acetal resin in the second layer issmaller than the amount of the plasticizer for 100 parts by weight ofthe polyvinyl acetal resin in the first layer.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, the second layer contains a polyvinylacetal resin and a plasticizer, and the amount of the plasticizer for100 parts by weight of the polyvinyl acetal resin in the second layer isnot less than 10 parts but not more than 45 parts by weight.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, a ratio of the thickness of the firstlayer to the thickness of the second layer is not less than 0.2 but notmore than 1.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, the second layer is laminated on thefirst surface of the first layer.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, the second layer contains a polyvinylacetal resin, the amount of the plasticizer for 100 parts by weight ofthe polyvinyl acetal resin in the first layer is 50 parts by weight ormore, a hydroxy group content of the polyvinyl acetal resin in the firstlayer is smaller than a hydroxy group content of the polyvinyl acetalresin in the second layer, a difference between the hydroxy groupcontent of the polyvinyl acetal resin in the first layer and the hydroxygroup content of the polyvinyl acetal resin in the second layer is 9.2mol % or less, and a degree of acetylation of the polyvinyl acetal resinin the first layer is 8 mol % or less if a difference between thehydroxy group content of the polyvinyl acetal resin in the first layerand the hydroxy group content of the polyvinyl acetal resin in thesecond layer is larger than 8.5 mol % but not larger than 9.2 mol %.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, the polyvinyl acetal resin in the firstlayer contains a high molecular weight component having an absolutemolecular weight of one million or more, and a proportion of the highmolecular weight component in the polyvinyl acetal resin in the firstlayer is 7.4% or more; or the polyvinyl acetal resin in the first layercontains a high molecular weight component having a molecular weight interms of polystyrene of one million or more, and a proportion of thehigh molecular weight component in the polyvinyl acetal resin in thefirst layer is 9% or more.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, in the case that the first layer is usedas a resin film and a viscoelasticity of the resin film is measured, aratio (G′(Tg+80)/G′(Tg+30)) of an elastic modulus G′(Tg+80) at (Tg+80)°C. to an elastic modulus G′(Tg+30) at (Tg+30)° C. is 0.65 or more,provided that Tg (° C.) represents a glass transition temperature of theresin film.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, in the case that a resin film contains100 parts by weight of the polyvinyl acetal resin contained in the firstlayer and 60 parts by weight of triethylene glycol di-2-ethylhexanoateas a plasticizer and a viscoelasticity of the resin film is measured, aratio (G′(Tg+80)/G′(Tg+30)) of an elastic modulus G′(Tg+80) at (Tg+80)°C. to an elastic modulus G′(Tg+30) at (Tg+30)° C. is 0.65 or more,provided that Tg (° C.) represents a glass transition temperature of theresin film.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, the polyvinyl acetal resin in the firstlayer is obtained by acetalizing a polyvinyl alcohol resin having anaverage degree of polymerization of more than 3000.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, the intermediate film further includes athird layer positioned on a second surface that is an opposite side ofthe first surface of the first layer.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, the third layer contains a polyvinylacetal resin, and a carbon number of the acetal group of the polyvinylacetal resin contained in the third layer is 3 or 4, a degree ofacetalization thereof is not less than 60 mol % but not more than 75 mol%, and a degree of acetylation thereof is 10 mol % or less.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, the third layer contains a polyvinylacetal resin and a plasticizer, and the amount of the plasticizer for100 parts by weight of the polyvinyl acetal resin in the third layer issmaller than the amount of the plasticizer for 100 parts by weight ofthe polyvinyl acetal resin in the first layer.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, the third layer contains a polyvinylacetal resin and a plasticizer, and the amount of the plasticizer for100 parts by weight of the polyvinyl acetal resin in the third layer isnot less than 10 parts but not more than 45 parts by weight.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, a ratio of the thickness of the firstlayer to the total thickness of the second layer and the third layer isnot less than 0.1 but not more than 0.5.

According to a specific aspect of the intermediate film for laminatedglass of the present invention, the third layer is laminated on thesecond surface of the first layer.

A laminated glass according to the present invention includes: a firstcomponent for laminated glass; a second component for laminated glass;and an intermediate film interposed between the first component forlaminated glass and the second component for laminated glass, whereinthe intermediate film is the intermediate film for laminated glassformed in accordance with the present invention.

Effect of the Invention

The intermediate film for laminated glass according to the presentinvention includes: a first layer containing a polyvinyl acetal resinand a plasticizer; and a second layer positioned on a first surface ofthe first layer. In a phase diagram of three values including a degreeof acetalization, a degree of acetylation, and a hydroxy group contentof the polyvinyl acetal resin contained in the first layer, the valuesof the degree of acetalization, the degree of acetylation, and thehydroxy group content each fall within a region surrounded by a lineincluding four straight lines connecting a first coordinate (degree ofacetalization:degree of acetylation:hydroxy group content=70 mol %:30mol %:0 mol %), a second coordinate (degree of acetalization:degree ofacetylation:hydroxy group content=34 mol %:30 mol %:36 mol %), a thirdcoordinate (degree of acetalization:degree of acetylation:hydroxy groupcontent=94 mol %:0 mol %:6 mol %), and a fourth coordinate (degree ofacetalization:degree of acetylation:hydroxy group content=100 mol %:0mol %:0 mol %) in the stated order. Accordingly, in a laminated glassincluding the intermediate film for laminated glass of the presentinvention, a sound-insulating property in a high frequency range can beenhanced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a phase diagram of three values including a degree ofacetalization, a degree of acetylation, and a hydroxy group content of apolyvinyl acetal resin contained in a first layer of an intermediatefilm for laminated glass according to the present invention, and shows aregion indicated by the values of the degree of acetalization, thedegree of acetylation, and the hydroxy group content.

FIG. 2 is a phase diagram of three values including a degree ofacetalization, a degree of acetylation, and a hydroxy group content ofthe polyvinyl acetal resin contained in the first layer of theintermediate film for laminated glass according to the presentinvention, and shows a preferable region indicated by the values of thedegree of acetalization, the degree of acetylation, and the hydroxygroup content.

FIG. 3 is a phase diagram of three values including a degree ofacetalization, a degree of acetylation, and a hydroxy group content ofthe polyvinyl acetal resin contained in the first layer of theintermediate film for laminated glass according to the presentinvention, and shows a preferable region indicated by the values of thedegree of acetalization, the degree of acetylation, and the hydroxygroup content.

FIG. 4 is a phase diagram of three values including a degree ofacetalization, a degree of acetylation, and a hydroxy group content ofthe polyvinyl acetal resin contained in the first layer of theintermediate film for laminated glass according to the presentinvention, and shows a preferable region indicated by the values of thedegree of acetalization, the degree of acetylation, and the hydroxygroup content.

FIG. 5 is a partially cutaway cross-sectional view schematicallyillustrating an intermediate film for laminated glass according to oneembodiment of the present invention.

FIG. 6 is a partially cutaway cross-sectional view schematicallyillustrating one example of a laminated glass including the intermediatefilm for laminated glass illustrated in FIG. 5.

FIG. 7 is a phase diagram of three values including a degree ofacetalization, a degree of acetylation, and a hydroxy group content of apolyvinyl acetal resin contained in a first layer of each ofintermediate films for laminated glass of Examples 1 to 7 andComparative Example 1, and indicates values of the degree ofacetalization, the degree of acetylation, and the hydroxy group content.

FIG. 8 is a phase diagram of three values including a degree ofacetalization, a degree of acetylation, and a hydroxy group content of apolyvinyl acetal resin contained in a first layer of each ofintermediate films for laminated glass of Examples 8 to 14 andComparative Example 2, and indicates values of the degree ofacetalization, the degree of acetylation, and the hydroxy group content.

FIG. 9 is a phase diagram of three values including a degree ofacetalization, a degree of acetylation, and a hydroxy group content of apolyvinyl acetal resin contained in a first layer of each ofintermediate films for laminated glass of Examples 15 to 35 andComparative Examples 3 and 4, and indicates values of the degree ofacetalization, the degree of acetylation, and the hydroxy group content.

FIG. 10 is a view for explaining a relation between the loss factor tanδ and the temperature and a relation between the elastic modulus G′ andthe temperature in the case that a resin film contains the polyvinylacetal resin contained in the first layer and triethylene glycoldi-2-ethylhexanoate and a viscoelasticity of the resin film is measured.

MODE(S) FOR CARRYING OUT THE INVENTION

The following will specifically discuss the present invention.

An intermediate film for laminated glass according to the presentinvention has a layered structure including at least two layers. Theintermediate film for laminated glass according to the present inventionincludes a first layer containing a polyvinyl acetal resin (hereinafter,also referred to as a polyvinyl acetal resin (1)) and a plasticizer(hereinafter, also referred to as a plasticizer (1)), and a second layerpositioned on a first surface side of the first layer. The intermediatefilm for laminated glass according to the present invention may be anintermediate film for laminated glass having a layered structure of twolayers including only the first layer and the second layer, or may be anintermediate film for laminated glass having a layered structure ofthree or more layers including the first layer, the second layer, andother layer(s).

In the case of the intermediate film for laminated glass according tothe present invention, in a phase diagram of three values including adegree X of acetalization, a degree Y of acetylation, and a hydroxygroup content Z of the polyvinyl acetal resin (1) in the first layer(the phase diagram of three values in FIG. 1), the values of the degreeX of acetalization, the degree Y of acetylation, and the hydroxy groupcontent Z are each fall within a region R1 surrounded by a line L1including four straight lines connecting a first coordinate A, a secondcoordinate B, a third coordinate C, and a fourth coordinate D (describedlater) in the stated order.

The first coordinate A (degree X of acetalization:degree Y ofacetylation:hydroxy group content Z=70 mol %:30 mol %:0 mol %)

The second coordinate B (degree X of acetalization:degree Y ofacetylation: hydroxy group content Z=34 mol %:30 mol %:36 mol %)

The third coordinate C (degree X of acetalization:degree Y ofacetylation:hydroxy group content Z=94 mol %:0 mol %:6 mol %)

The fourth coordinate D (degree X of acetalization:degree Y ofacetylation:hydroxy group content Z=100 mol %:0 mol %:0 mol %)

The line L1 includes four straight lines of a straight line connectingthe first coordinate A and the second coordinate B, a straight lineconnecting the second coordinate B and the third coordinate C, astraight line connecting the third coordinate C and the fourthcoordinate D, and a straight line connecting the fourth coordinate D andthe first coordinate A.

In the case of the intermediate film for laminated glass according tothe present invention, in the phase diagram of three values illustratedin FIG. 1, the values of the degree X of acetalization, the degree Y ofacetylation, and the hydroxy group content Z of the polyvinyl acetalresin (1) each fall within the region R1 surrounded by the line L1illustrated in FIG. 1. The degree X of acetalization, the degree Y ofacetylation, and the hydroxy group content Z of the polyvinyl acetalresin (1) each may be a value on the line L1 illustrated in FIG. 1.

According to the main feature of the present invention, a first layercontaining a polyvinyl acetal resin (1) and a plasticizer (1), and asecond layer positioned on a first surface side of the first layer areprovided, and in the phase diagram of three values illustrated in FIG.1, the values of the degree X of acetalization, the degree Y ofacetylation, and the hydroxy group content Z of the polyvinyl acetalresin (1) contained in the first layer each fall within the region R1surrounded by the line L1 illustrated in FIG. 1.

In recent years, fuel automobiles using internal-combustion engines arebeing switched over to electric vehicles using electric motors, hybridelectric vehicles using internal-combustion engines and electric motors,and the like. Laminated glasses used for fuel automobiles usinginternal-combustion engines are particularly required to have asound-insulating property against sounds in a relatively low frequencyrange. Of course, it is preferable that laminated glasses used for fuelautomobiles using internal-combustion engines also have a highsound-insulating property against sounds in a high frequency range. Incontrast, laminated glasses used for electric vehicles and hybridelectric vehicles utilizing electric motors are particularly required tohave a high sound-insulating property against sounds in a high frequencyrange in order to effectively insulate driving sounds of their electricmotors.

The present inventors found that the sound-insulating property of alaminated glass in a high frequency range is effectively andsufficiently increased when the values of the degree X of acetalization,the degree Y of acetylation, and the hydroxy group content Z of thepolyvinyl acetal resin (1) contained in the first layer each fall withinthe region R1.

Especially, a first layer containing the polyvinyl acetal resin (1) thathas values of the degree X of acetalization, the degree Y ofacetylation, and the hydroxy group content Z within the region R1enhances the sound-insulating property in a temperature range of 20 to30° C.

In the region R1, the degree Y of acetylation of the polyvinyl acetalresin (1) is 30 mol % or less. When the degree Y of acetylation is 30mol % or less, productivity of the polyvinyl acetal resin (1) isimproved.

From the standpoint of further enhancing the sound-insulating propertyof an intermediate film and a laminated glass, in a phase diagram ofthree values including the degree X of acetalization, the degree Y ofacetylation, and the hydroxy group content Z of the polyvinyl acetalresin (1) (phase diagram of three values illustrated in FIG. 2), thevalues of the degree X of acetalization, the values of the degree Y ofacetylation, and the hydroxy group content Z each preferably fall withina region R2 surrounded by a line L2 including four straight linesconnecting the first coordinate A, the second coordinate B, a fifthcoordinate E (described later), and the fourth coordinate D in thestated order.

The fifth coordinate E (degree of acetalization:degree ofacetylation:hydroxy group content=95 mol %:0 mol %:5 mol %)

The line L2 includes four straight lines of a straight line connectingthe first coordinate A and the second coordinate B, a straight lineconnecting the second coordinate B and the fifth coordinate E, astraight line connecting the fifth coordinate E and the fourthcoordinate D, and a straight line connecting the fourth coordinate D andthe first coordinate A.

In the case of the intermediate film for laminated glass according tothe present invention, in the phase diagram of three values illustratedin FIG. 2, values of the degree X of acetalization, the degree Y ofacetylation, and the hydroxy group content Z of the polyvinyl acetalresin (1) each preferably fall within the region R2 surrounded by theline L2 illustrated in FIG. 2. The degree X of acetalization, the degreeY of acetylation, and the hydroxy group content Z of the polyvinylacetal resin (1) each may be a value on the line L2.

From the standpoint of further enhancing the sound-insulating propertyof an intermediate film and a laminated glass, in the phase diagram ofthree values including the degree X of acetalization, the degree Y ofacetylation, and the hydroxy group content Z of the polyvinyl acetalresin (1) (phase diagram of three values illustrated in FIG. 3), thevalues of the degree X of acetalization, the degree Y of acetylation,and the hydroxy group content Z each preferably fall within a region R3surrounded by a line L3 including four straight lines connecting thefirst coordinate A, the second coordinate B, the third coordinate C, anda sixth coordinate F (described later) in the stated order.

The sixth coordinate F (degree of acetalization:degree ofacetylation:hydroxy group content=95 mol %:5 mol %:0 mol %)

The line L3 includes four straight lines of a straight line connectingthe first coordinate A and the second coordinate B, a straight lineconnecting the second coordinate B and the third coordinate C, astraight line connecting the third coordinate C and the sixth coordinateF, and a straight line connecting the sixth coordinate F and the firstcoordinate A.

In the case of the intermediate film for laminated glass according tothe present invention, in the phase diagram of three values illustratedin FIG. 3, the values of the degree X of acetalization, the degree Y ofacetylation, and the hydroxy group content Z of the polyvinyl acetalresin (1) each preferably fall within the region R3 surrounded by theline L3 illustrated in FIG. 3. The degree X of acetalization, the degreeY of acetylation, and the hydroxy group content Z of the polyvinylacetal resin (1) each may be a value on the line L3 illustrated in FIG.3.

In the region R3, the degree X of acetalization of the polyvinyl acetalresin (1) is 95 mol % or less, and may be 94 mol % or less. When thedegree X of acetalization is 95 mol % or less, the productivity of thepolyvinyl acetal resin (1) is improved.

From the standpoint of further enhancing the sound-insulating propertyof an intermediate film and a laminated glass, in the diagram of threevalues including the degree X of acetalization, the degree Y ofacetylation, and the hydroxy group content Z of the polyvinyl acetalresin (1) (phase diagram of three values illustrated in FIG. 4), thevalues of the degree X of acetalization, the degree Y of acetylation,and the hydroxy group content Z each preferably fall within a region R4surrounded by a line L4 including four straight lines connecting thefirst coordinate A, the second coordinate B, the fifth coordinate E, andthe sixth coordinate F in the stated order.

The line L4 includes four straight lines of a straight line connectingthe first coordinate A and the second coordinate B, a straight lineconnecting the second coordinate B and the fifth coordinate E, astraight line connecting the fifth coordinate E and the sixth coordinateF, and a straight line connecting the sixth coordinate F and the firstcoordinate A.

In the case of the intermediate film for laminated glass of the presentinvention, in the phase diagram of three values illustrated in FIG. 4,the values of the degree X of acetalization, the degree Y ofacetylation, the hydroxy group content Z of the polyvinyl acetal resineach preferably fall within the region R4 surrounded by the line L4illustrated in FIG. 4. The degree X of acetalization, the degree Y ofacetylation, and the hydroxy group content Z of the polyvinyl acetalresin (1) each may be a value on the line L4 illustrated in FIG. 4.

In the region R4, the degree X of acetalization of the polyvinyl acetalresin (1) is 95 mol % or less. When the degree X of acetalization is 95mol % or less, the productivity of the polyvinyl acetal resin (1) isimproved.

In the following, the present invention is specifically described withreference to drawings by means of specific embodiments and examples ofthe present invention.

FIG. 5 illustrates a partially cutaway cross-sectional viewschematically illustrating a laminated glass including an intermediatefilm for laminated glass according to one embodiment of the presentinvention.

An intermediate film 1 illustrated in FIG. 5 is a multilayerintermediate film. The intermediate film 1 is used for production of alaminated glass. The intermediate film 1 is an intermediate film forlaminated glass. The intermediate film 1 includes a first layer 2, asecond layer 3 positioned on the side of a first surface 2 a of thefirst layer 2, and a third layer 4 positioned on the side of a secondsurface 2 b of the first layer 2 which is an opposite side of the firstsurface 2 a. The second layer 3 is laminated on the first surface 2 a ofthe first layer 2. The third layer 4 is laminated on the second surface2 b of the first layer 2. The first layer 2 is an intermediate layer andmainly functions as a sound-insulating layer. The second layer 3 and thethird layer 4 are protective layers and are surface layers in thepresent embodiment. The first layer 2 is positioned between the secondlayer 3 and the third layer 4. The first layer 2 is interposed betweenthe second layer 3 and the third layer 4. Accordingly, the intermediatefilm 1 has a multilayer structure in which the second layer 3, the firstlayer 2, and the third layer 4 are laminated in the stated order.

It is to be noted that other layers may be laminated between the firstlayer 2 and the second layer 3, and between the first layer 2 and thethird layer 4. Preferably, the second layer 3 is directly laminated onthe first layer 2, and the first layer 2 is directly laminated on thethird layer 4. Examples of other layers include a layer containing athermoplastic resin such as polyvinyl acetal resin, and a layercontaining polyethylene terephthalate and the like.

The first layer 2 contains the polyvinyl acetal resin (1) and theplasticizer (1). The second layer 3 contains preferably a thermoplasticresin, more preferably a polyvinyl acetal resin, and still morepreferably a polyvinyl acetal resin and a plasticizer. The third layer 4contains preferably a thermoplastic resin, more preferably a polyvinylacetal resin, and still more preferably a polyvinyl acetal resin and aplasticizer. It is preferred that the composition of the first layer 2is different from each composition of second layer 3 and the third layer4. The compositions of the second layer 3 and the third layer 4 may bethe same as or different from each other.

In the case of the intermediate film 1, the values of the degree X ofacetalization, the degree Y of acetylation, and the hydroxy groupcontent Z of the polyvinyl acetal resin (1) contained in the first layer2 each fall within the region R1, and therefore, the sound-insulatingproperty of a laminated glass including the intermediate film 1 in ahigh frequency range can be enhanced. In the case of the intermediatefilm 1, the values of the degree X of acetalization, the degree Y ofacetylation, and the hydroxy group content Z of the polyvinyl acetalresin (1) contained in the first layer 2 each fall within the region R2,R3, or R4, and therefore, the sound-insulating property of a laminatedglass including the intermediate film 1 in a high frequency range can befurther enhanced and the productivity of the intermediate film 1 isimproved.

In the intermediate film 1, the second layer 3 and the third layer 4 arelaminated on the faces of the first layer 2. A second layer ispositioned on the side of a first surface of a first layer, and thesecond layer is preferably laminated on the first surface of the firstlayer. The second layer may be positioned only on the side of the firstsurface of the first layer and a third layer may not be positioned onthe side of a second surface of the first layer. Preferably, the secondlayer is positioned on the side of the first surface of the first layerand the third layer is positioned on the side of the second surface ofthe first layer. The third layer is preferably laminated on the secondsurface of the first layer. When the third layer is laminated on thesecond surface of the first layer, the penetration resistance of alaminated glass including the intermediate film 1 can be furtherenhanced.

In an intermediate film for laminated glass having a multilayerstructure in which the sound-insulating property is enhanced, bubbleformation may easily occur in a laminated glass. In studies for solvingsuch a problem, the present inventors found the following. In anintermediate film for laminated glass having a multilayer structure, aplasticizer migrates among layers, leading to formation of a layerhaving a large plasticizer content. For example, a plasticizer maymigrate from a second layer and a third layer to a first layer toincrease the plasticizer content of the first layer. Moreover, if alayer having a large plasticizer content is formed, namely, theplasticizer content of the first layer increases, bubble formation islikely to occur in a laminated glass including the intermediate film forlaminated glass, and bubble formation once occurs, the generated bubblestend to serve as cores and thereby to cause bubble growth.

From the standpoint of suppressing bubble formation and bubble growth inthe laminated glass, the following conditions are preferable. Namely,preferably, the amount of the plasticizer for 100 parts by weight of thepolyvinyl acetal resin in the first layer 2 is 50 parts by weight ormore, the hydroxy group content of the polyvinyl acetal resin in thefirst layer 2 is smaller than the hydroxy group content of the polyvinylacetal resin in the second layer 3, a difference (hereinafter, alsoreferred to as difference (1-2) in content) between the hydroxy groupcontent of the polyvinyl acetal resin in the first layer 2 and thehydroxy group content of the polyvinyl acetal resin in the second layer3 is 9.2 mol % or less, and the degree of acetylation of the polyvinylacetal resin in the first layer 2 is 8 mol % or less if a difference(difference (1-2) in content) between the hydroxy group content of thepolyvinyl acetal resin in the first layer 2 and the hydroxy groupcontent of the polyvinyl acetal resin in the second layer 3 is not lessthan 8.5 mol % but not more than 9.2 mol %. The difference (1-2) incontent may be more than 8.5 mol % but not more than 9.2 mol %, andfurther may be 8.5 mol % or less.

Also preferably, the hydroxy group content of the polyvinyl acetal resinin the first layer 2 is smaller than the hydroxy group content of thepolyvinyl acetal resin in the third layer 4, a difference (hereinafter,also referred to as difference (1-3) in content) between the hydroxygroup content of the polyvinyl acetal resin in the first layer 2 and thehydroxy group content of the polyvinyl acetal resin in the third layer 4is 9.2 mol % or less, and the degree of acetylation of the polyvinylacetal resin in the first layer 2 is 8 mol % or less if the difference(difference (1-3) in content) between the hydroxy group content of thepolyvinyl acetal resin in the first layer 2 and the hydroxy groupcontent of the polyvinyl acetal resin in the third layer 4 is more than8.5 mol % but not more than 9.2 mol %. Even though the difference (1-3)in content is 8.5 mol % or less, when the difference (1-2) in content ismore than 8.5 mol % but not more than 9.2 mol %, the degree ofacetylation of the polyvinyl acetal resin in the first layer 2 ispreferably 8 mol % or less. The difference (1-3) in content may be morethan 8.5 mol % but not more than 9.2 mol %, and further may be 8.5 mol %or less.

As a result of the intensive studies for suppressing bubble formationand bubble growth, the present inventors found that controlling thehydroxy group content of the polyvinyl acetal resin in each of the firstlayer, the second layer and the third layer as mentioned abovesufficiently suppresses bubble formation and bubble growth in alaminated glass. Since migration of a plasticizer is suppressed andbubble formation and bubble growth are sufficiently suppressed in alaminated glass, the plasticizer content of each layer, especially theplasticizer content of the first layer 2, can be increased. Accordingly,the sound-insulating property of a laminated glass is further enhanced.

If the amount of the plasticizer for 100 parts by weight of thepolyvinyl acetal resin in the first layer 2 is larger than the amount ofthe plasticizer for 100 parts by weight of the polyvinyl acetal resin ineach of the second layer 3 and the third layer 4, bubble formation ismore likely to occur. Further, bubble formation once occurs, thegenerated bubbles tend to serve as cores and thereby to cause bubblegrowth. In contrast, controlling the hydroxy group content of thepolyvinyl acetal resin in each of the first layer, the second layer andthe third layer as mentioned above sufficiently suppresses bubbleformation and bubble growth in a laminated glass.

From the standpoint of further suppressing bubble formation and bubblegrowth in a laminated glass, the lower limit of each of the differences(difference (1-2) in content and difference (1-3) in content) betweenthe hydroxy group content of the polyvinyl acetal resin in the firstlayer 2 and each of the hydroxy group contents of the polyvinyl acetalresin in the second layer 3 and the third layer 4 is preferably 0.1 mol%, more preferably 1 mol %, and still more preferably 2 mol %, whereasthe upper limit thereof is preferably 8.5 mol %, more preferably 7.8 mol%, still more preferably 7 mol %, and particularly preferably 5.6 mol %.Since bubble formation and bubble growth in a laminated glass arefurther suppressed, the lower limit of each of the differences(difference (1-2) in content and difference (1-3) in content) betweenthe hydroxy group content of the polyvinyl acetal resin in the firstlayer 2 and each of the hydroxy group contents of the polyvinyl acetalresin in the second layer 3 and the third layer 4 is preferably 5 mol %or less, more preferably 4.5 mol % or less, still more preferably 4 mol% or less, and particularly preferably 3.5 mol % or less.

Preferably, the polyvinyl acetal resin in the first layer 2 contains ahigh molecular weight component (hereinafter, also referred to as a highmolecular weight component X) having an absolute molecular weight of onemillion or more, or the polyvinyl acetal resin in the first layer 2contains a high molecular weight component (hereinafter, also referredto as a high molecular weight component Y) having a molecular weight interms of polystyrene (hereinafter, also referred to as a molecularweight y) of one million or more. The high molecular weight component Xand the high molecular weight component Y are polyvinyl acetal resins.Preferably, the proportion of the high molecular weight component X inthe polyvinyl acetal resin in the first layer 2 is 7.4% or more, or theproportion of the high molecular weight component Y in the polyvinylacetal resin in the first layer 2 is 9% or more.

When the high molecular weight component X having an absolute molecularweight of one million or more in the polyvinyl acetal resin in the firstlayer 2 is the specific proportion, bubble formation in a laminatedglass is suppressed. Also, when the high molecular weight component Yhaving a molecular weight y of one million or more in the polyvinylacetal resin in the first layer 2 is the specific proportion, bubbleformation in a laminated glass is suppressed.

The proportion of the high molecular weight component X in the polyvinylacetal resin in the first layer 2 is defined by a value in a percentage(%) indicating a proportion of the area of a region corresponding to thehigh molecular weight component X in the peak area of the polyvinylacetal resin element which is obtained in measurement of the absolutemolecular weight. The proportion of the high molecular weight componentY in the polyvinyl acetal resin in the first layer 2 is defined by avalue in percentage (%) indicating an area of a region corresponding tothe high molecular weight component Y in the peak area of the polyvinylacetal resin element which is obtained in measurement of the molecularweight in terms of polystyrene.

Compositions of the second layer 3 and the third layer 4 each arepreferably different from the composition of the first layer 2. Thepolyvinyl acetal resin in each of the second layer 3 and the third layer4 may contain a high molecular weight component X having an absolutemolecular weight of one million or more, and the proportion of the highmolecular weight component X in the polyvinyl acetal resin in each ofthe second layer 3 and the third layer 4 may be 7.4% or more.Alternatively, the polyvinyl acetal resin in each of the second layer 3and the third layer 4 may contain a high molecular weight component Yhaving a molecular weight y of one million or more, and the proportionof the high molecular weight component Y in the polyvinyl acetal resinin each of the second layer 3 and the third layer 4 may be 9% or more.

From the standpoint of further enhancing the sound-insulating propertyof the laminated glass and further suppressing bubble formation andbubble growth, the lower limit of the proportion of the high molecularweight component X having an absolute molecular weight of one million ormore in the polyvinyl acetal resin in the first layer 2 is preferably8%, more preferably 8.5%, still more preferably 9%, particularlypreferably 9.5%, and most preferably 10%. Since the sound-insulatingproperty of the laminated glass can be further enhanced and bubbleformation and bubble growth are further suppressed, the proportion ofthe high molecular weight component X is preferably 11% or more, morepreferably 12% or more, still more preferably 14% or more, andparticularly preferably 16% or more. The upper limit of the proportionof the high molecular weight component X is, though not particularlylimited, preferably 40%, more preferably 30%, and still more preferably25%.

In the case where the polyvinyl acetal resin in the first layer 2contains the high molecular weight component Y having a molecular weighty of one million or more, the lower limit of the proportion of highmolecular weight component Y having a molecular weight y of one millionor more in the polyvinyl acetal resin in the first layer 2 that containsthe high molecular weight component Y is preferably 10%, more preferably11%, still more preferably 11.5%, and particularly preferably 12%. Sincethe sound-insulating property of a laminated glass is further enhancedand bubble formation and bubble growth are further suppressed, theproportion of the high molecular weight component Y is preferably 12.5%or more, more preferably 13.5% or more, still more preferably 14% ormore, particularly preferably 15% or more, and most preferably 18% ormore. The upper limit of the proportion of the high molecular weightcomponent Y is, though not particularly limited, preferably 40%, morepreferably 30%, and still more preferably 25%. When the proportion ofthe high molecular weight component Y satisfies the above lower limit,the sound-insulating property of the laminated glass is furtherenhanced, and bubble formation and bubble growth are further suppressed.

In the case that a resin film A contains 100 parts by weight of thepolyvinyl acetal resin contained in the first layer 2 and 60 parts byweight of triethylene glycol di-2-ethylhexanoate (3GO) as a plasticizerand a viscoelasticity of the resin film A is measured (test method A), aratio (G′(Tg+80)/G′(Tg+30)) of an elastic modulus G′(Tg+80) at (Tg+80)°C. to an elastic modulus G′(Tg+30) at (Tg+30)° C. is preferably 0.65 ormore, provided that Tg (° C.) represents a glass transition temperatureof the resin film A.

In the case that the first layer is used as a resin film and aviscoelasticity of the resin film B is measured (test method B), a ratio(G′(Tg+80)/G′(Tg+30)) of an elastic modulus G′(Tg+80) at (Tg+80)° C. toan elastic modulus G′(Tg+30) at (Tg+30)° C. is preferably 0.65 or more,provided that Tg (° C.) represents a glass transition temperature of theresin film B.

In the test method B, the first layer 2 is used as the resin film B, andthe first layer 2 itself is the resin film B.

The resin film B is the first layer 2 and contains the polyvinyl acetalresin and the plasticizer at a weight ratio as that in the first layer2. In the test method B, the elastic modulus G′(Tg+80) and the elasticmodulus G′(Tg+30) are measured preferably after migration of theplasticizer in the intermediate film 1 for laminated glass. In the testmethod B, the elastic modulus G′(Tg+80) and the elastic modulusG′(Tg+30) are measured preferably after storage of the intermediate film1 for laminated glass at a humidity of 30% (±3%) and at a temperature of23° C. for a month so that the plasticizer is migrated in theintermediate film 1 for laminated glass.

As a result of intensive studies for suppressing bubble formation andbubble growth, the present inventors found that when the ratio(G′(Tg+80)/G′(Tg+30)) in the test method A or the test method B is 0.65or more, bubble formation and bubble growth in a laminated glass aresufficiently suppressed. Since bubble formation and bubble growth in alaminated glass are sufficiently suppressed even when the plasticizercontent of the first layer 2 is large, the sound-insulating property ofthe laminated glass is enhanced. Especially, when the intermediate film1 for laminated glass include the second layer 3 and the third layer 4laminated on the faces of the first layer and the ratio(G′(Tg+80)/G′(Tg+30)) is controlled to 0.65 or more, bubble formationand bubble growth in a laminated glass using intermediate film 1 isfurther suppressed.

The ratio (G′(Tg+80)/G′(Tg+30)) is 0.65 or more but preferably 1.0 orless. when a ratio (G′(Tg+80)/G′(Tg+30)) is 0.65 or more, even when alaminated glass is stored under significantly severe conditions for along time, bubble formation and bubble growth in the laminated glass aresufficiently suppressed. When a ratio (G′(Tg+80)/G′(Tg+30)) satisfiesthe lower limit and the upper limit, even when a laminated glass isstored under significantly severe conditions for a long time, bubbleformation and bubble growth in the laminated glass are furthereffectively suppressed.

From the standpoint of further enhancing the sound-insulating propertyof a laminated glass, the amount of the plasticizer for 100 parts byweight of the polyvinyl acetal resin in the first layer 2 is preferably40 parts by weight or more. Even when the plasticizer content in thefirst layer is large, bubble formation and bubble growth in thelaminated glass are suppressed by forming the first layer to have aratio (G′(Tg+80)/G′(Tg+30)) of 0.65 or more.

The glass transition temperature Tg (° C.) indicates a peak temperatureof loss factor tan δ obtained from the measurement of theviscoelasticity. From the standpoint of further suppressing bubbleformation and bubble growth in a laminated glass, the ratio(G′(Tg+80)/G′(Tg+30)) is more preferably not less than 0.7 but not morethan 0.95, and still more preferably not less than 0.75 but not morethan 0.9. Especially, in the case where the ratio (G′(Tg+80)/G′(Tg+30))is controlled by the average degree of polymerization of the polyvinylalcohol resin, the ratio (G′(Tg+80)/G′(Tg+30)) is preferably 0.65 ormore, more preferably 0.66 or more, still more preferably 0.67 or more,and particularly preferably 0.7 or more, but is preferably 0.82 or lessand more preferably 0.8 or less. In such a case, bubble formation andbubble growth in a laminated glass are sufficiently suppressed and thesound-insulating property of a laminated glass is further enhanced.Moreover, when the ratio (G′(Tg+80)/G′(Tg+30)) is 0.82 or less or 0.8 orless, an intermediate film is easily formed.

Examples of a method for controlling the ratio (G′(Tg+80)/G′(Tg+30)) to0.65 or more in the test method A or the test method B include a methodof using a polyvinyl alcohol resin with a relatively high average degreeof polymerization in synthesis of a polyvinyl acetal resin in the firstlayer 2, and a method of enhancing the mutual influence betweenmolecules of the polyvinyl acetal resin in the first layer 2. Examplesof the method of enhancing the mutual influence between molecules of thepolyvinyl acetal resin in the first layer 2 include a method ofphysically or chemically crosslinking molecules of the polyvinyl acetalresin. In particular, since the intermediate film 1 can be easily formedusing an extruder, preferred are a method of using a polyvinyl alcoholresin with a relatively high average degree of polymerization insynthesis of a polyvinyl acetal resin in the first layer 2, and a methodof physically crosslinking molecules of the polyvinyl acetal resin.

A description is given on an example of a relation between the lossfactor tan δ obtained by measurement of the viscoelasticity andtemperature and a relation between an elastic modulus G′ andtemperature, with reference to FIG. 10.

The loss factor tan δ and temperature have a relation as shown in FIG.10. The temperature of the loss factor tan δ at a peak P is the glasstransition temperature Tg.

In FIG. 10, the glass transition temperature Tg in the case of theelastic modulus G′ indicated by a dashed line A2 and the glasstransition temperature Tg in the case of the elastic modulus G′indicated by a solid line A1 are the same temperature. On the basis ofthe elastic modulus G′(Tg+30), for example, as a change D in the elasticmodulus G′(Tg+80) is smaller, bubble formation and bubble growth in alaminated glass are more effectively suppressed. A change D1 in theelastic modulus G′ indicated by the solid line A1 is smaller than achange D2 in the elastic modulus G′ indicated by the dashed line A2.Accordingly, in FIG. 10, bubble formation and bubble growth in alaminated glass are effectively suppressed in the case of the elasticmodulus G′ indicated by the solid line A1 with a relatively small changeD1, than in the case of the elastic modulus G′ indicated by the dashedline A2 with a relatively large change D2.

The G′(Tg+30) is preferably 200,000 Pa or more. The G′(Tg+30) is morepreferably 220,000 Pa or more, still more preferably 230,000 Pa or more,and particularly preferably 240,000 Pa or more, but is preferably10,000,000 Pa or less, more preferably 5,000,000 Pa or less, sill morepreferably 1,000,000 Pa or less, particularly preferably 500,000 Pa orless, and most preferably 300,000 Pa or less. When a G′(Tg+30) is equalto or higher than the above lower limit, bubble formation and bubblegrowth in a laminated glass are more effectively suppressed.

The relation between the elastic modulus G′ and temperature is greatlyinfluenced by the kind of the polyvinyl acetal resin, especiallyinfluenced by the average degree of polymerization of the polyvinylalcohol resin used for obtaining the polyvinyl acetal resin, not so muchinfluenced by the kind of the plasticizer, and not so much influenced bythe amount of the plasticizer if it is within a reasonable amount as aplasticizer. In the case where a plasticizer is changed from 3GO to aplasticizer such as monobasic organic acid esters other than 3GO,especially in the case where triethylene glycol di-2-ethyl butyrate(3GH) and triethylene glycol di-n-heptanoate (3G7) are used asplasticizers, the ratio (G′(Tg+80)/G′(Tg+30)) is not so different fromthe ratio (G′(Tg+80)/G′(Tg+30)) in the case of using 3GO. Also, in thecase where the amount of the plasticizer for 100 parts by weight of thepolyvinyl acetal resin is 50 to 80 parts by weight, the ratio(G′(Tg+80)/G′(Tg+30)) is not so different. The ratio(G′(Tg+80)/G′(Tg+30)) of a resin film containing 100 parts by weight ofa polyvinyl acetal resin and 60 parts by weight of triethylene glycoldi-2-ethylhexanoate (3GO) as a plasticizer is not so much different fromthe ratio (G′(Tg+80)/G′(Tg+30)) of the first layer 2. Although the bothratios (G′(Tg+80)/G′(Tg+30)) obtained in the test method A and the testmethod B are preferably 0.65 or more, the ratio (G′(Tg+80)/G′(Tg+30))obtained in the test method B is more preferably 0.65 or more.

Also, for suppressing bubble formation in an intermediate film forlaminated glass, the polyvinyl acetal resin in the first layer 2 ispreferably obtained by acetalization of a polyvinyl alcohol resin havingan average degree of polymerization of more than 3000. In such a case,the ratio (G′(Tg+80)/G′(Tg+30)) may not be 0.65 or more, but ispreferably 0.65 or more. From the standpoint of further suppressingbubble formation and bubble growth in a laminated glass, the amount ofthe plasticizer in the first layer 2 is preferably 40 parts by weight ormore for 100 parts by weight of the polyvinyl acetal resin in the firstlayer 2 which is obtained by acetalization of a polyvinyl alcohol resinhaving an average degree of polymerization of more than 3000. Moreover,from the standpoint of further suppressing bubble formation and bubblegrowth in a laminated glass, the hydroxy group content of polyvinylacetal resin in the first layer 2 which is obtained by acetalization ofa polyvinyl alcohol resin having an average degree of polymerization ofmore than 3000 is preferably 30 mol % or less.

From the standpoint of further enhancing the sound-insulating propertyof a laminated glass, the amount of the plasticizer for 100 parts byweight of the polyvinyl acetal resin in the first layer 2 is preferably40 parts by weight or more, more preferably 50 parts by weight or more,still more preferably 55 parts by weight or more, and particularlypreferably 60 parts by weight or more. Even when the amount of theplasticizer in the first layer 2 is large as above, bubble formation andbubble growth in a laminated glass are more effectively suppressed bycontrolling the hydroxy group content of each of the polyvinyl acetalresins in the first layer, the second layer and the third layer asmentioned above, by controlling the proportion of the high molecularweight component X having an absolute molecular weight of one million ormore or the proportion of the high molecular weight component Y having amolecular weight y of one million or more, or by controlling the ratio(G′(Tg+80)/G′(Tg+30)).

In the following, specific descriptions are given on the first layer,the second layer and the third layer included in the intermediate filmfor laminated glass according to the present invention, and on thepolyvinyl acetal resins and plasticizers contained in the first layer,the second layer and the third layer.

(Thermoplastic Resin)

The first layer contains a polyvinyl acetal resin (1). The second layerpreferably contains a thermoplastic resin and more preferably contains apolyvinyl acetal resin (hereinafter, also referred to as polyvinylacetal resin (2)). The third layer preferably contains a thermoplasticresin and more preferably contains a polyvinyl acetal resin(hereinafter, also referred to as a polyvinyl acetal resin (3)). Whenthe thermoplastic resins contained in the second layer and the thirdlayer are the polyvinyl acetal resin (2) and the polyvinyl acetal resin(3), adhesiveness between the second layer or the third layer andcomponents for laminated glass is sufficiently high.

Examples of the thermoplastic resins include polyvinyl acetal resin,ethylene-vinyl acetate copolymer resin, ethylene-acrylic copolymerresin, polyurethane resin, and polyvinyl alcohol resin. Thermoplasticresins other than these may be used.

The polyvinyl acetal resin (1), the polyvinyl acetal resin (2) and thepolyvinyl acetal resin (3) are obtained, for example, by acetalizationof polyvinyl alcohol resins with aldehydes. The polyvinyl alcohol resinsare obtained, for example, by saponification of polyvinyl acetate. Adegree of saponification of the polyvinyl alcohol resin is commonlywithin a range of 70 to 99.9 mol %, preferably within a range of 75 to99.8 mol %, and more preferably within a range of 80 to 99.8 mol %.

An average degree of polymerization of the polyvinyl alcohol resin forobtaining each of the polyvinyl acetal resin (1), the polyvinyl acetalresin (2) and the polyvinyl acetal resin (3) is preferably 200 or more,more preferably 500 or more, still more preferably 1600 or more,particularly preferably 2600 or more, and most preferably 2700 or more,but is preferably 5000 or less, more preferably 4000 or less, and stillmore preferably 3500 or less. When the average degree of polymerizationis equal to or higher than the lower limit, the penetration resistanceof a laminated glass is further enhanced. When the average degree ofpolymerization is equal to or lower than the upper limit, anintermediate film is easily formed.

From the standpoint of further enhancing the penetration resistance of alaminated glass, the average degree of polymerization of the polyvinylalcohol resin is especially preferably 2700 or more but not more than5000.

From the standpoint of further suppressing bubble formation and bubblegrowth in a laminated glass, the lower limit of the average degree ofpolymerization of the polyvinyl alcohol resin used for obtaining thepolyvinyl acetal resin (1) in the first layer is preferably 3010,preferably 3050, preferably 3500, preferably 3600, preferably 4000,preferably 4050, whereas the upper limit thereof is preferably 7000,preferably 6000, preferably 5000, preferably 4900, and preferably 4500.Especially, for the purpose of further suppressing bubble formation andbubble growth in a laminated glass, sufficiently enhancing thesound-insulating property of the laminated glass, and easily forming anintermediate film, the average degree of polymerization of the polyvinylalcohol resin used for obtaining the polyvinyl acetal resin (1) in thefirst layer is preferably 3010 or more and more preferably 3020 or more,but preferably 4000 or less, more preferably less than 4000, still morepreferably 3800 or less, particularly preferably 3600 or less, and mostpreferably 3500 or less.

The polyvinyl acetal resin (2) in the second layer and the polyvinylacetal resin (3) in the third layer are obtained by acetalization ofpolyvinyl alcohol resin. The lower limit of the average degree ofpolymerization of the polyvinyl alcohol resin for obtaining each of thepolyvinyl acetal resin (2) in the second layer and the polyvinyl acetalresin (3) in the third layer is preferably 200, more preferably 500,still more preferably 1000, and particularly preferably 1500, whereasthe upper limit is preferably 4000, more preferably 3500, still morepreferably 3000, and particularly preferably 2500. When the averagedegree of polymerization is equal to or higher than the preferably lowerlimit, the penetration resistance of a laminated glass is furtherenhanced. When the average degree of polymerization is equal to or lowerthan the preferable upper limit, an intermediate film is easily formed.

The average degree of polymerization of the polyvinyl alcohol resin usedfor obtaining the polyvinyl acetal resin (1) in the first layer ispreferably higher, preferably higher by 500 or more, preferably higherby 800 or more, more preferably higher by 1000 or more, still morepreferably higher by 1300 or more, and particularly preferably higher by1800 or more than that of the polyvinyl alcohol resin used for obtainingeach of the polyvinyl acetal resin (2) in the second layer and thepolyvinyl acetal resin (3) in the third layer.

The average degree of polymerization of the polyvinyl alcohol resin isdetermined by a method in conformity with JIS K6726 “Testing methods forpolyvinyl alcohol”.

The carbon number of an acetal group in the polyvinyl acetal resin isnot particularly limited. The aldehyde used in production of thepolyvinyl acetal resin is not particularly limited. The carbon number ofan acetal group in the polyvinyl acetal resin is preferably 3 to 5, andmore preferably 3 or 4. When the carbon number of an acetal group in thepolyvinyl acetal resin is 3 or more, the glass transition temperature ofan intermediate film is sufficiently low and the sound-insulatingproperty against solid sounds at low temperatures are further enhanced.

The aldehyde is not particularly limited. Commonly, a C1 to C10 aldehydeis suitably used. Examples of the C1-10 aldehydes includepropionaldehyde, n-butyl aldehyde, isobutyl aldehyde, n-valeraldehyde,2-ethyl butyl aldehyde, n-hexylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decyl aldehyde, formaldehyde, acetaldehyde, andbenzaldehyde. Preferred among these are propionaldehyde, n-butylaldehyde, isobutyl aldehyde, n-hexylaldehyde, and n-valeraldehyde. Morepreferred are propionaldehyde, n-butyl aldehyde, and isobutyl aldehyde.Still more preferred is n-butyl aldehyde. Each of these aldehydes may beused alone, or two or more of these may be used in combination.

The polyvinyl acetal resin is preferably polyvinyl butyral resin. Theintermediate film for laminated glass according to the present inventionpreferably contains polyvinyl butyral resin as each of the polyvinylacetal resins contained in the first layer, the second layer and thethird layer. The polyvinyl butyral resin is easily synthesized. Use ofthe polyvinyl butyral resin allows exertion of adhesiveness of theintermediate film to components for laminated glass more appropriately.In addition, light resistance and weather resistance are furtherenhanced.

A hydroxy group content (amount of hydroxy groups) of the polyvinylacetal resin (1) is 0 mol % or more but not more than 36 mol %. When thehydroxy group content is equal to or lower than the upper limit, thesound-insulating property of a laminated glass in a high frequency rangeis enhanced, and the flexibility of an intermediate film may increase,and thus the intermediate film can be easily handled. From thestandpoint of further enhancing the sound-insulating property of alaminated glass in a high frequency range, the hydroxy group content(amount of hydroxy groups) of the polyvinyl acetal resin (1) is morepreferably 35 mol % or less, still more preferably 30 mol % or less,particularly preferably 25 mol % or less, particularly preferably 20 mol% or less, particularly preferably 15 mol % or less, and particularlypreferably 10 mol % or less. From the standpoint of enhancing thesound-insulating property of a laminated glass in a high frequencyrange, the hydroxy group content of the polyvinyl acetal resin (1) ispreferably lower. The hydroxy group content of the polyvinyl acetalresin (1) may be 0 mol %.

A hydroxy group content (amount of hydroxy groups) of each of thepolyvinyl acetal resin (2) and the polyvinyl acetal resin (3) ispreferably not less than 20 mol % but not more than 50 mol %. When thehydroxy group content is equal to or higher than the lower limit, thepenetration resistance of a laminated glass is further enhanced. Whenthe hydroxy group content is equal to or lower than the upper limit, theplasticizer hardly bleeds out. In addition, the flexibility of anintermediate film may increase, and thus the intermediate film can beeasily handled. From the standpoint of further enhancing thesound-insulating property of a laminated glass, a hydroxy group content(amount of hydroxy groups) of each of the polyvinyl acetal resin (2) andthe polyvinyl acetal resin (3) is preferably 25 mol % or more, morepreferably 28 mol % or more, and particularly preferably 30 mol % ormore, but more preferably 45 mol % or less, more preferably 40 mol % orless, and particularly preferably 35 mol % or less.

From the standpoint of further enhancing the sound-insulating propertyof a laminated glass, the hydroxy group content of the polyvinyl acetalresin (1) in the first layer is lower than the hydroxy group content ofeach of the polyvinyl acetal resin (2) in the second layer and thepolyvinyl acetal resin (3) in the third layer. From the standpoint offurther enhancing the sound-insulating property of a laminated glass,the hydroxy group content of the polyvinyl acetal resin (1) in the firstlayer is lower than the hydroxy group content of each of the polyvinylacetal resin (2) in the second layer and the polyvinyl acetal resin (3)in the third layer preferably by 1 mol % or more, more preferably by 3mol % or more, still more preferably by 5 mol % or more, particularlypreferably by 7 mol % or more, particularly preferably by 10 mol % ormore, particularly preferably by 15 mol % or more, and particularlypreferably by 20 mol % or more.

Each of the hydroxy group contents of the polyvinyl acetal resin (1),the polyvinyl acetal resin (2) and the polyvinyl acetal resin (3) is avalue of a mol fraction in percentage (mol %) which is obtained bydivision of the amount of ethylene groups bonded with hydroxy groups bythe total amount of ethylene groups of the main chain. The amount ofethylene groups bonded with hydroxy groups, for example, is determinedby measurement in conformity with JIS K6726 “Testing methods forpolyvinyl alcohol”.

The degree of acetylation (amount of acetyl groups) of the polyvinylacetal resin (1) is 0 mol % or more but not more than 30 mol %. From thestandpoint of further enhancing the sound-insulating property of alaminated glass in a high frequency range, the degree of acetylation(amount of acetyl groups) of the polyvinyl acetal resin (1) ispreferably 10 mol % or more, more preferably 15 mol % or more, andparticularly preferably 20 mol % or more, but more preferably 28 mol %or less and still more preferably 25 mol % or less.

A degree of acetylation of each of the polyvinyl acetal resin (2) andthe polyvinyl acetal resin (3) is 0 mol % or more but not more than 10mol %. When the degree of acetylation is equal to or lower than theupper limit, the sound-insulating property of a laminated glass in ahigh frequency range is further enhanced, and the intermediate film hasbetter strength and better mechanical properties. From the standpoint offurther enhancing the sound-insulating property of a laminated glass ina high frequency range, the degree of acetylation of each of thepolyvinyl acetal resin (2) and the polyvinyl acetal resin (3) ispreferably 8 mol % or less and more preferably less than 3 mol %. Thedegree of acetylation of each of the polyvinyl acetal resin (2) and thepolyvinyl acetal resin (3) is preferably 0.1 mol % or more andparticularly preferably 2 mol % or less. When the degree of acetylationof each of the polyvinyl acetal resin (2) and the polyvinyl acetal resin(3) is less than 3 mol %, the mechanical properties of the intermediatefilm are further improved. As a result, the penetration resistance ofthe laminated glass is further enhanced.

The degree of acetylation is obtained below. The amount of ethylenegroups bonded with the acetal group and the amount of the ethylenegroups bonded with the hydroxyl group are subtracted from the totalamount of ethylene groups in the main chain. The obtained value isdivided by the total amount of ethylene groups in the main chain. Theobtained mole fraction expressed as percentage is the degree ofacetylation. The amount of the ethylene groups bonded with acetal groupsis determined by measurement in conformity with JIS K6728 “Testingmethods for polyvinyl butyral”.

The degree of acetalization (degree of butyralization in the case of apolyvinyl butyral resin) of the polyvinyl acetal resin (1) is preferably34 mol % or more, preferably 40 mol % or more, and more preferably 45mol % or more, but is 100 mol % or less, preferably 95 mol % or less,more preferably 80 mol % or less, still more preferably 75 mol % orless, and particularly preferably 65 mol % or less. When the degree ofacetalization is equal to or higher than the lower limit, thecompatibility between the polyvinyl acetal resin (1) and the plasticizeris enhanced, so that the bleed out of the plasticizer is suppressed.When the degree of acetalization is equal to or lower than the upperlimit, the reaction time needed for production of the polyvinyl acetalresin (1) is shortened.

A degree of acetalization (degree of butyralization in the case of apolyvinyl butyral resin) of each of the polyvinyl acetal resin (2) andthe polyvinyl acetal resin (3) is preferably 55 mol % or more, morepreferably 60 mol % or more, and still more preferably 63 mol % or more,but of preferably 85 mol % or less, more preferably 75 mol % or less,and still more preferably 70 mol % or less. When the degree ofacetalization is equal to or higher than the lower limit, thecompatibility between the polyvinyl acetal resin (2) or the polyvinylacetal resin (3) and the plasticizer is enhanced. When the degree ofacetalization is equal to or lower than the upper limit, the reactiontime required for production of each of the polyvinyl acetal resin (2)and the polyvinyl acetal resin (3) is shortened.

The degree of acetalization is a value of the mol fraction in percentage(mol %) which is obtained by division of the amount of ethylene groupsbonded with acetal groups by the total amount of ethylene groups of themain chain.

The degree of acetalization is determined as follows. The degree ofacetylation (amount of acetyl groups) and the hydroxy group content(amount of vinyl alcohol) are measured by a method in conformity withJIS K6728 “Testing methods for polyvinyl butyral”. The measured valuesare converted to mol fractions. The obtained degree of acetylation andthe hydroxy group content are subtracted from 100 mol %.

In the case of a polyvinyl acetal resin and the case where a polyvinylacetal resin is a polyvinyl butyral resin, the degree of acetalization(degree of butyralization) and the degree of acetylation are obtainablefrom the measurement results by a method in conformity with JIS K6728“Testing methods for polyvinyl butyral” or ASTM D1396-92. Themeasurement in conformity with ASTM D1396-92 is preferable.

Since migration of the plasticizer is easily controlled and thesound-insulating property of a laminated glass is further enhanced, whenthe difference (1-2) in content is 8.5 mol % or less, the degree ofacetylation of the polyvinyl acetal resin (1) in the first layer ispreferably more than 8 mol %. Since migration of the plasticizer iseasily controlled and the sound-insulating property of a laminated glassis further enhanced, when the difference (1-3) in content is 8.5 mol %or less, the degree of acetylation of the polyvinyl acetal resin (1) inthe first layer is preferably more than 8 mol %.

Since migration of the plasticizer is easily controlled and thesound-insulating property of a laminated glass is further enhanced, whenthe difference (1-2) in content is more than 8.5 mol % but not more than9.2 mol % or when the difference (1-2) in content is not more than 9.2mol %, preferably, the degree of acetalization of the polyvinyl acetalresin (1) in the first layer is 68 mol % or more or the hydroxy groupcontent thereof is less than 31.5 mol %. Since migration of theplasticizer is easily controlled and the sound-insulating property of alaminated glass is further enhanced, when the difference (1-3) incontent is more than 8.5 mol % but not more than 9.2 mol % or when thedifference (1-3) in content is not more than 9.2 mol %, preferably, thedegree of acetalization of the polyvinyl acetal resin (1) in the firstlayer is 68 mol % or more or the hydroxy group content thereof is lessthan 31.5 mol %.

Moreover, since bubble formation and bubble growth in a laminated glassare further suppressed and the sound-insulating property of a laminatedglass is further enhanced, the polyvinyl acetal resin (1) in the firstlayer is preferably a polyvinyl acetal resin having a degree ofacetylation of less than 8 mol % (hereinafter, also referred to as“polyvinyl acetal resin A”) or a polyvinyl acetal resin having a degreeof acetylation of 8 mol % or more (hereinafter, also referred to as“polyvinyl acetal resin B”).

The degree of acetylation a of the polyvinyl acetal resin A is less than8 mol %, preferably 7.5 mol % or less, preferably 7 mol % or less,preferably 6 mol % or less, preferably 5 mol % or less, but ofpreferably 0.1 mol % or more, preferably 0.5 mol % or more, preferably0.8 mol % or more, preferably 1 mol % or more, preferably 2 mol % ormore, preferably 3 mol % or more, and preferably 4 mol % or more. Whenthe degree of acetylation a satisfies the upper limit and the lowerlimit, the compatibility between the polyvinyl acetal resin and theplasticizer is further enhanced and the sound-insulating property of alaminated glass is further enhanced.

The lower limit of the degree of acetalization a of the polyvinyl acetalresin A is preferably 68 mol %, more preferably 70 mol %, still morepreferably 71 mol %, and particularly preferably 72 mol %, and has anupper limit of preferably 85 mol %, more preferably 83 mol %, still morepreferably 81 mol %, and particularly preferably 79 mol %. When thedegree of acetalization a is equal to or higher than the lower limit,the sound-insulating property of a laminated glass is further enhanced.When the degree of acetalization a is equal to or lower than the upperlimit, the reaction time required for production of the polyvinyl acetalresin A is shortened.

A hydroxy group content a of the polyvinyl acetal resin A is preferably30 mol % or less, preferably 27.5 mol % or less, preferably 27 mol % orless, preferably 26 mol % or less, preferably 25 mol % or less,preferably 24 mol % or less, and preferably 23 mol % or less, but ofpreferably 16 mol % or more, preferably 18 mol % or more, preferably 19mol % or more, and preferably 20 mol % or more. When the hydroxy groupcontent a is equal to or lower than the upper limit, thesound-insulating property of a laminated glass is further enhanced. Whenthe hydroxy group content a is equal to or higher than the lower limit,the adhesiveness of an intermediate film is further enhanced.

The polyvinyl acetal resin A is preferably a polyvinyl butyral resin.

A degree of acetylation b of the polyvinyl acetal resin B is preferably8 mol % or more, preferably 9 mol % or more, preferably 10 mol % ormore, preferably 11 mol % or more, and preferably 12 mol % or more, butof preferably 30 mol % or less, preferably 28 mol % or less, preferably26 mol % or less, preferably 24 mol % or less, preferably 20 mol % orless, and preferably 19.5 mol % or less. When the degree of acetylationb is equal to or higher than the lower limit, the sound-insulatingproperty of a laminated glass is further enhanced. When the degree ofacetylation b is equal to or lower than the upper limit, the reactiontime required for production of the polyvinyl acetal resin B isshortened. Especially, since the reaction time required for productionof the polyvinyl acetal resin B is further shortened, a degree ofacetylation b of the polyvinyl acetal resin B is preferably less than 20mol %.

The lower limit of the degree of acetalization b of the polyvinyl acetalresin B is preferably 50 mol %, more preferably 52.5 mol %, still morepreferably 54 mol %, and particularly preferably 60 mol %, whereas theupper limit thereof is preferably 80 mol %, more preferably 77 mol %,still more preferably 74 mol %, and particularly preferably 71 mol %.When the degree of acetalization b is equal to or higher than the lowerlimit, the sound-insulating property of a laminated glass is furtherenhanced. When the degree of acetalization b is equal to or lower thanthe upper limit, the reaction time required for production of thepolyvinyl acetal resin B is shortened.

A hydroxy group content b of the polyvinyl acetal resin B is preferably30 mol % or less, preferably 27.5 mol % or less, preferably 27 mol % orless, preferably 26 mol % or less, and preferably 25 mol % or less, butof preferably 18 mol % or more, preferably 20 mol % or more, preferably22 mol % or more, and preferably 23 mol % or more. When the hydroxygroup content b is equal to or lower than the upper limit, thesound-insulating property of a laminated glass is further enhanced. Whenthe hydroxy group content b is equal to or higher than the lower limit,the adhesiveness of an intermediate film is further enhanced.

The polyvinyl acetal resin B is preferably a polyvinyl butyral resin.

The polyvinyl acetal resin A and the polyvinyl acetal resin B each arepreferably obtained by acetalization of a polyvinyl alcohol resin havingan average degree of polymerization of more than 3000 with an aldehyde.The aldehyde is preferably a C1-10 aldehyde and is more preferably C4-5aldehyde. The lower limit of the average degree of polymerization of thepolyvinyl alcohol resin is preferably 3010, preferably 3050, preferably3500, preferably 3600, preferably 4000, preferably 4050, whereas theupper limit thereof is preferably 7000, preferably 6000, preferably5000, preferably 4900, and preferably 4500. The polyvinyl acetal resin Aand the polyvinyl acetal resin B in the first layer each areparticularly preferably obtained by acetalization of a polyvinyl alcoholresin having an average degree of polymerization of more than 3000 butless than 4000. Especially, since bubble formation and bubble growth ina laminated glass are further suppressed, the sound-insulating propertyof a laminated glass is sufficiently enhanced, and an intermediate filmis easily formed, an average degree of polymerization of the polyvinylalcohol resin used for production of each of the polyvinyl acetal resinA and the polyvinyl acetal resin B in the first layer is preferably 3010or more and more preferably 3020 or more, but of preferably 4000 orless, more preferably less than 4000, still more preferably 3800 orless, particularly preferably 3600 or less, and most preferably 3500 orless.

The lower limit of the weight average molecular weight of each of thepolyvinyl acetal resin (1), the polyvinyl acetal resin (2) and thepolyvinyl acetal resin (3) is preferably 100,000, and more preferably300,000, whereas the upper limit thereof is preferably 10,000,000 andmore preferably 5,000,000. When the weight average molecular weight ofthe polyvinyl acetal resin is equal to or lower than the preferablelower limit, the strength of the intermediate film may be lowered. Whenthe weight average molecular weight of the polyvinyl acetal resin ishigher than the preferable upper limit, the strength of the resultingintermediate film may be too much. The weight average molecular weightrefers to a weight average molecular weight in terms of polystyrenebased on the measurement by gel permeation chromatography (GPC).

The weight average molecular weight and the number average molecularweight respectively refer to the weight average molecular weight and thenumber average molecular weight in terms of polystyrene determined bygel permeation chromatography (GPC). For measurement of the weightaverage molecular weight and the number average molecular weight interms of polystyrene, for example, GPC measurement of a polystyrenestandard sample having a known molecular weight is carried out. Thepolystyrene standard samples used (“Shodex Standard SM-105”, “ShodexStandard SH-75” from Showadenkosha. co., ltd.) are 14 pieces of sampleshaving weight average molecular weights of 580, 1,260, 2,960, 5,000,10,100, 21,000, 28,500, 76,600, 196,000, 630,000, 1,130,000, 2,190,000,3,150,000, and 3,900,000. The molecular weights relative to the elutiontimes indicated by the peak tops of the standard sample peaks areplotted so that an approximate straight line is drawn. The approximatestraight line is used as a calibration curve. A multilayer intermediatefilm left in a constant temperature and humidity room (humidity of 30%(±3%), temperature of 23° C.) is divided into surface layers (the secondlayer and the third layer) and an intermediate layer (the first layer).The peeled first layer (intermediate layer) is dissolved intetrahydrofuran (THF) to give a 0.1% by weight solution. The solutionwas analyzed using a GPC device for measurement of the weight averagemolecular weight and the number average molecular weight. An exemplaryGPC device is a GPC device (Hitachi High-Technologies Corp. “RI: L2490,auto sampler: L-2200, pump: L-2130, column oven: L-2350, column:GL-A120-S and GL-A100MX-S in series”) connected with a light scatteringdetector for GPC (VISCOTEK, “Model 270 (RALS+VISCO)”).

(Production Method of a Polyvinyl Acetal Resin Containing a HighMolecular Weight Component X Having an Absolute Molecular Weight of OneMillion or More or a High Molecular Weight Component Y Having aMolecular Weight Y of One Million or More)

The following will discuss a specific production method of a polyvinylacetal resin containing a high molecular weight component X having anabsolute molecular weight of one million or more or a high molecularweight component Y having a molecular weight y of one million or morewhich is one example of the polyvinyl acetal resin containing a highmolecular weight component X having an absolute molecular weight of onemillion or more or a high molecular weight component Y having amolecular weight y of one million or more at a proportion satisfying theabove lower limit.

A polyvinyl alcohol resin is first prepared. The polyvinyl alcohol resinis obtained by, for example, saponifying polyvinyl acetate. The degreeof saponification of the polyvinyl alcohol resin is commonly in a rangeof 70 to 99.9 mol %, preferably in a range of 75 to 99.8 mol %, and morepreferably in a range of 80 to 99.8 mol %.

The lower limit of the average degree of polymerization of the polyvinylalcohol resin is preferably 200, more preferably 500, still morepreferably 1,000, and particularly preferably 1,500, whereas the upperlimit thereof is preferably 3,000, more preferably 2,900, still morepreferably 2,800, and particularly preferably 2,700. If the averagedegree of polymerization is too low, the penetration resistance of alaminated glass tends to be lowered. If the average degree ofpolymerization is too high, an intermediate film may be hardly formed.

The polyvinyl alcohol resin is reacted with an aldehyde using a catalystfor acetalization thereof. In this operation, a solution containing thepolyvinyl alcohol resin may be used. Exemplary solvents used for thesolution containing the polyvinyl alcohol resin include water.

The production method of the polyvinyl acetal resin contained in thefirst layer is preferably a method in which a polyvinyl alcohol resin isreacted with an aldehyde using a catalyst for acetalization thereof,thereby giving a polyvinyl acetal resin.

The production method of the first layer preferably includes the stepsof: reacting a polyvinyl alcohol resin with an aldehyde using a catalystfor acetalization of the polyvinyl alcohol resin, thereby producing apolyvinyl acetal resin; and preparing the first layer using a mixturecontaining the resulting polyvinyl acetal resin and a plasticizer. Inthe step of preparing a first layer or after preparation of the firstlayer, a second layer is laminated on the first layer, and a third layeris further laminated, if necessary, thereby preparing a multilayerintermediate film. Alternatively, a first layer and a second layer maybe co-extruded to produce a multilayer intermediate film. Also, a firstlayer, a second layer, and a third layer may be co-extruded to produce amultilayer intermediate film.

The aldehyde is not particularly limited. Commonly, a C1-10 aldehyde issuitably used. Examples of the C1-10 aldehyde include propionaldehyde,n-butyl aldehyde, isobutyl aldehyde, n-valeraldehyde, 2-ethyl butylaldehyde, n-hexylaldehyde, n-octylaldehyde, n-nonyl aldehyde, n-decylaldehyde, formaldehyde, acetaldehyde, and benzaldehyde. Particularly,n-butyl aldehyde, n-hexylaldehyde, and n-valeraldehyde are preferred,and n-butyl aldehyde is more preferred. Each of the aldehydes may beused alone, or two or more of them may be used in combination.

From the standpoint of easily obtaining a polyvinyl acetal resincontaining a high molecular weight component X having an absolutemolecular weight of one million or more or a high molecular weightcomponent Y having a molecular weight y of one million or more,exemplified are a method in which, for example, before or during anacetalization reaction using an aldehyde, a crosslinking agent such asdialdehyde is added for crosslinking main chains of adjacent polyvinylalcohol resins, a method in which an excessive amount of an aldehyde isadded to promote acetalization among molecules, and a method in which apolyvinyl alcohol resin having a high degree of polymerization is added.Each of these methods may be used alone, or two or more of them may beused in combination.

The catalyst is preferably an acid catalyst. Examples thereof includenitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, andparatoluene sulfonic acid.

The molecular weight in terms of polystyrene refers to the molecularweight in terms of polystyrene determined by gel permeationchromatography (GPC). The proportion (%) of the high molecular weightcomponent Y having a molecular weight y of one million or more in thepolyvinyl acetal resin is calculated based on the proportion of the areacorresponding to the region where the molecular weight y is one millionor more in the peak area detected by an RI detector in measurement ofthe molecular weight in terms of polystyrene of the polyvinyl acetalresin by GPC. The peak area refers to an area between the peak and thebase line of an element to be measured.

The molecular weight in terms of polystyrene is determined as follows,for example.

For measurement of the molecular weight in terms of polystyrene, GPCmeasurement of a polystyrene standard sample having a known molecularweight is carried out. The polystyrene standard samples used (“ShodexStandard SM-105”, “Shodex Standard SH-75” from Showadenkosha. co., ltd.)are 14 pieces of samples having weight average molecular weights of 580,1,260, 2,960, 5,000, 10,100, 21,000, 28,500, 76,600, 196,000, 630,000,1,130,000, 2,190,000, 3,150,000, and 3,900,000. The weight averagemolecular weight relative to the elution times indicated by the peaktops of the standard sample peaks are plotted so that an approximationstraight line is drawn. The approximation straight line is used as acalibration curve. For example, in the case of measuring a proportion(%) of the high molecular weight component Y having a molecular weight yof one million or more in the polyvinyl acetal resin in an intermediatelayer of a multilayer intermediate film that includes a second layer(surface layer), a first layer (intermediate layer), and a third layer(surface layer) laminated in the stated order, a multilayer intermediatefilm left in a constant temperature and humidity room (humidity of 30%(±3%), temperature of 23° C.) is divided into surface layers and anintermediate layer. The peeled intermediate layer is dissolved intetrahydrofuran (THF) to give a 0.1% by weight solution. The solutionwas analyzed using a GPC device for measurement of the peak area of thepolyvinyl acetal resin in the intermediate layer. Based on the elutiontime of the polyvinyl acetal resin in the intermediate layer and thecalibration curve, an area corresponding to a region where the molecularweight in terms of polystyrene of the polyvinyl acetal resin in theintermediate layer is one million or more is calculated. The areacorresponding to a region where the molecular weight in terms ofpolystyrene of the polyvinyl acetal resin in the intermediate layer isone million or more is divided by the peak area of the polyvinyl acetalresin in the intermediate layer, and the obtained value is expressed ina percentage (%). In this manner, the proportion of the high molecularweight component Y having a molecular weight y of one million or more inthe polyvinyl acetal resin is calculated. The molecular weight in termsof polystyrene is measured, for example, using a Gel PermeationChromatography (GPC) device (Hitachi High-Technologies Corp. “RI: L2490,auto sampler: L-2200, pump: L-2130, column oven: L-2350, column:GL-A120-S and GL-A100MX-S in series”).

(Plasticizer)

The first layer contains a plasticizer (1). The second layer preferablycontains a plasticizer (hereinafter, also referred to as a plasticizer(2)). The third layer preferably contains a plasticizer (hereinafter,also referred to as a plasticizer (3)). The plasticizer (1), plasticizer(2) and plasticizer (3) usable in the first layer, the second layer andthe third layer are not particularly limited. Conventionally knownplasticizers may be used as the plasticizer (1), plasticizer (2) andplasticizer (3). One plasticizer may be used or two or more plasticizersmay be used in combination for the plasticizer (1), plasticizer (2) andplasticizer (3).

Examples of the plasticizer (1), plasticizer (2) and plasticizer (3)include organic ester plasticizers such as monobasic organic acid estersand polybasic organic acid esters, and phosphoric acid plasticizers suchas organophosphate plasticizers and organophosphite plasticizers. Inparticular, organic ester plasticizers are preferable. The plasticizersare preferably liquid plasticizers.

The monobasic organic acid esters are not particularly limited, andexamples thereof include glycol esters obtained by a reaction betweenglycols and monobasic organic acids, and esters of triethylene glycol ortripropylene glycol and monobasic organic acids. Examples of the glycolsinclude triethylene glycol, tetraethylene glycol, and tripropyleneglycol. Examples of the monobasic organic acids include butyric acid,isobutyric acid, caproic acid, 2-ethylbutyric acid, heptylic acid,n-octylic acid, 2-ethylhexanoic acid, n-nonylic acid, and decylic acid.

The polybasic organic acid esters are not particularly limited, andexamples thereof include ester compounds of polybasic organic acids withlinear or branched C4-8 alcohols. Examples of the polybasic organicacids include adipic acid, sebacic acid, and azelaic acid.

The organic ester plasticizers are not particularly limited, andexamples thereof include triethylene glycol di-2-ethyl butyrate,triethylene glycol di-2-ethylhexanoate, triethylene glycol dicaprylate,triethylene glycol di-n-octanoate, triethylene glycol di-n-heptanoate,tetraethylene glycol di-n-heptanoate, dibutyl sebacate, dioctylazelate,dibutyl carbitol adipate, ethylene glycol di-2-ethyl butyrate,1,3-propylene glycol di-2-ethyl butyrate, 1,4-butylene glycol di-2-ethylbutyrate, diethylene glycol di-2-ethyl butyrate, diethylene glycoldi-2-ethyl hexanoate, dipropylene glycol di-2-ethyl butyrate,triethylene glycol di-2-ethylpentanoate, tetraethylene glycoldi-2-ethylbutyrate, diethylene glycol dicaprylate, dihexyl adipate, dioctyladipate, hexylcyclohexyl adipate, mixture of heptyl adipate and nonyladipate, diisononyl adipate, diisodecyl adipate, heptylnonyl adipate,dibutyl sebacate, oil-modified alkyd sebacate, and mixture of phosphateester and adipic acid ester. Organic ester plasticizers other than thesemay be used.

The organophosphate plasticizers are not particularly limited, andexamples thereof include tributoxyethyl phosphate, isodecylphenylphosphate, and triisopropyl phosphate.

The plasticizer (1), plasticizer (2) and plasticizer (3) are preferablydiester plasticizers represented by the formula (1).

R1 and R2 in the formula (1) each represent a C5-10 organic group, R3represents an ethylene group, isopropylene group or n-propylene group,and p represents an integer of 3 to 10.

The plasticizer preferably contains at least one of triethylene glycoldi-2-ethylhexanoate (3GO) and triethylene glycol di-2-ethylbutyrate(3GH), and more preferably contains triethylene glycoldi-2-ethylhexanoate.

The plasticizer (i), plasticizer (2) and plasticizer (3) are preferablyplasticizers having a SP value of 13.5 to 14.5. Use of a plasticizerhaving a SP value of 13.5 to 14.5 effectively enhances thesound-insulating property of a laminated glass in a high frequencyrange. More preferably, a SP value of the plasticizer (1) is 13.5 to14.5.

The “SP value” is calculated by the Fedors method (R. F. Fedors, Polym.Eng. Sci., 14, 147 (1974)). When the SP value is within the above range,the compatibility between the plasticizer and the polyvinyl acetal resinis fine.

From the standpoint of further enhancing the sound-insulating propertyof an intermediate film and a laminated glass, the plasticizer (1),plasticizer (2) and plasticizer (3) are also preferably diesterplasticizers represented by the formula (2). Accordingly, theplasticizer is preferably a diester plasticizer represented by theformula (1) or a diester plasticizer represented by the formula (2).

R1 and R2 in the formula (2) each represent an organic group having atleast one ether bond, and n represents an integer of 2 to 8.

From the standpoint of further enhancing the sound-insulating propertyof an intermediate film and a laminated glass, R1 and R2 in the formula(2) each preferably have at least one ether bond structural unitrepresented by the formula (11) or the formula (12).

From the standpoint of further enhancing the sound-insulating propertyof an intermediate film and a laminated glass, the plasticizer (1),plasticizer (2) and plasticizer (3) are preferably diester plasticizersrepresented by the formula (2A).

R21 and R26 in the formula (2A) each represent a C1-10 alkyl group, R22and R27 each represent a C1-10 alkylene group, m1 and m2 each representan integer of 1 to 5, and n represents an integer of 2 to 8.

Specific examples of the R1 and R2 in the case where they each are anorganic group having at least one ether bond include 2-butoxyethyl,2-(2-butoxyethoxy)ethyl, 2-[2-(2-butoxyethoxy)ethoxy]ethyl group. The R1and R2 each may be a group other than these.

The amount of the plasticizer (1) for 100 parts by weight of thepolyvinyl acetal resin (1) in the first layer is preferably 25 parts byweight or more, more preferably 30 parts by weight or more, and stillmore preferably 45 parts by weight or more, but is preferably 75 partsby weight or less, more preferably 70 parts by weight or less, stillmore preferably 60 parts by weight or less, particularly preferably 55parts by weight or less, and most preferably 50 parts by weight or less.When the amount of the plasticizer (1) is equal to or higher than thelower limit, the flexibility of an intermediate film may increase, andthus the intermediate film can be easily handled. When the amount of theplasticizer (1) is equal to or lower than the upper limit, thetransparency of an intermediate film is further enhanced.

The amount of the plasticizer (2) for 100 parts by weight of thepolyvinyl acetal resin (2) in the second layer (2) is preferably 10parts by weight or more, more preferably 15 parts by weight or more,still more preferably 20 parts by weight or more, particularlypreferably 25 parts by weight or more, and most preferably 30 parts byweight or more, but is preferably 45 parts by weight or less, and morepreferably 40 parts by weight or less. The amount of the plasticizer (3)for 100 parts by weight of the polyvinyl acetal resin (3) in the thirdlayer (3) is preferably 10 parts by weight or more, more preferably 15parts by weight or more, still more preferably 20 parts by weight ormore, particularly preferably 25 parts by weight or more, and mostpreferably 30 parts by weight or more, but is preferably 45 parts byweight or less and more preferably 40 parts by weight or less. When theamounts of the plasticizer (2) and the plasticizer (3) each is equal toor higher than the lower limit, the flexibility of an intermediate filmmay increase, and thus the intermediate film can be easily handled. Whenthe amounts of the plasticizer (2) and the plasticizer (3) each areequal to or lower than the upper limit, the penetration resistance of anintermediate film is further enhanced.

The amount of the plasticizer (2) (hereinafter, also referred to as theamount (2)) for 100 parts by weight of the polyvinyl acetal resin (2) inthe second layer is preferably smaller than the amount of theplasticizer (1) (hereinafter, also referred to as the amount (1)) for100 parts by weight of the polyvinyl acetal resin (1) in the firstlayer. The amount of the plasticizer (3) (hereinafter, also referred toas the amount (3)) for 100 parts by weight of the polyvinyl acetal resin(3) in the third layer is preferably smaller than the amount of theplasticizer (1) (hereinafter, also referred to as the amount (1)) for100 parts by weight of the polyvinyl acetal resin (1) in the firstlayer. When the amount (2) and the amount (3) are smaller than theamount (1), the penetration resistance of a laminated glass is furtherenhanced.

The difference between the amount (1) and the amount (2) or the amount(3) is preferably 1 part by weight or more, more preferably 3 parts byweight or more, and still more preferably 5 parts by weight or more, butis preferably 30 parts by weight or less, more preferably 25 parts byweight or less, and still more preferably 20 parts by weight or less.When the difference between the amount (1) and the amount (2) or theamount (3) is equal to or higher than the lower limit, thesound-insulating property of a laminated glass is further enhanced. Whenthe difference between the amount (1) and the amount (2) or the amount(3) is equal to or lower than the upper limit, the penetrationresistance of a laminated glass is further enhanced. The differencebetween the amount (1) and the amount (2) or the amount (3) is anumerical value obtained by subtracting the amount (2) or the amount (3)from the amount (1).

(Other Components)

The intermediate film for laminated glass according to the presentinvention may optionally contain additives such as ultravioletabsorbers, antioxidants, light stabilizers, flame retardants, antistaticagents, pigments, dyes, adhesion modifiers, damp proofing agents,fluorescent brighteners, and infrared absorbers. Each of these additivesmay be used alone, or two or more of them may be used in combination.

(Intermediate Film for Laminated Glass)

From the standpoint of further enhancing the sound-insulating propertyof a laminated glass at low temperatures and in a high frequency range,in the intermediate film for laminated glass according to the presentinvention, a peak temperature of tan δ which appears at the lowesttemperature measured at a frequency of 1 Hz is 0° C. or lower.

From the standpoint of further enhancing the sound-insulating propertyof a laminated glass in a high frequency range, a maximum value of tan δat a peak temperature of tan δ which appears at the lowest temperaturemeasured at a frequency of 1 Hz is 1.15 or more.

A thickness of the first layer is preferably 0.02 mm or more and morepreferably 0.05 mm or more, but preferably 1.8 mm or less and morepreferably 0.5 mm or less. With a thickness within such a preferablerange, the obtained intermediate film is not too thick, and thesound-insulating property of the resulting intermediate film and thelaminated glass is further enhanced.

A thickness of each the second layer and the third layer is preferably0.1 mm or more and more preferably 0.2 mm or more, but preferably 1 mmor less and more preferably 0.5 mm or less. When the thickness of eachof the second layer and the third layer satisfies the lower limit andthe upper limit, the resulting intermediate film is not too thick, thesound-insulating property of the resulting intermediate film and thelaminated glass is further enhanced, and the bleed out of theplasticizer is suppressed.

The ratio of a thickness T1 of the first layer to a thickness T2 of thesecond layer is preferably 0.15 or more and more preferably 0.2 or more,but is preferably 1 or less and more preferably 0.9 or less. Namely, inthe intermediate film where the thickness (μm) of the first layer is T1and the thickness (μm) of the second layer is T2, T1/T2 that is a ratioof the thickness of the first layer to the thickness of the second layeris preferably 0.4 to 1. In such a case, the sound-insulating property ofa laminated glass including the intermediate film in a high frequencyrange is further enhanced. Especially, the sound-insulating property ina high frequency range exceeding 3 kHz is effectively enhanced.

From the standpoint of further enhancing the sound-insulating propertyof a laminated glass in a high frequency range, the ratio (T1/T2) ismore preferably not less than 0.5 but not more than 0.9.

A ratio of the thickness of the first layer to the total thickness ofthe second layer and the third layer is preferably 0.1 to 0.5. In otherwords, in an intermediate film where the thickness (μm) of the firstlayer is T1, the thickness (μm) of the second layer is T2, the thickness(μm) of the third layer is T3, T1/(T2+T3) that is a ratio of thethickness of the first layer to the total thickness of the second layerand the third layer is preferably 0.1 to 0.5. In such a case, thesound-insulating property of a laminated glass including theintermediate film is further enhanced in a high frequency range.Especially, the sound-insulating property in a high frequency rangeexceeding 3 kHz is effectively enhanced.

From the standpoint of further enhancing the sound-insulating propertyof a laminated glass in a high frequency range, the ratio (T1/(T2+T3))is more preferably 0.12 or more and still more preferably 0.15 or more.

The intermediate film for laminated glass according to the presentinvention has a thickness of preferably 0.1 mm or more and morepreferably 0.25 mm or more, but of preferably 3 mm or less and morepreferably 1.5 mm or less. When the thickness of the intermediate filmis equal to or higher than the lower limit, the penetration resistanceof an intermediate film and a laminated glass is sufficiently enhanced.When the thickness of the intermediate film is equal to or lower thanthe upper limit, the transparency of an intermediate film is furtherenhanced.

The production method of the intermediate film for laminated glassaccording to the present invention is not particularly limited, and aconventionally known method may be employed. For example, a polyvinylacetal resin, a plasticizer, and other components added optionally arekneaded and formed into an intermediate film. An extrusion moldingmethod is preferable because it is suitable for continuous production.

The kneading method is not particularly limited. Exemplary methodsinclude a method using an extruder, plastograph, kneader, Banbury mixer,or calender roll. In particular, a method using an extruder ispreferable, and a method using a twin-screw extruder is more preferablebecause it is suitable for continuous production. The intermediate filmfor laminated glass according to the present invention may be producedby separately preparing a first layer, a second layer and a third layer,and then laminating the first layer, the second layer and the thirdlayer for production of a multilayer intermediate film. Alternatively,the intermediate film for laminated glass according to the presentinvention may be produced by co-extrusion of a first layer, a secondlayer and a third layer for lamination thereof.

The second layer and the third layer preferably contain the samepolyvinyl acetal resin because the production efficiency of theintermediate film is excellent in such a case. The second layer and thethird layer more preferably contain the same polyvinyl acetal resin andthe same plasticizer. The second layer and the third layer are stillmore preferably formed by using the same resin composition.

(Laminated Glass)

FIG. 6 illustrates one example of a laminated glass including anintermediate film for laminated glass according to one embodiment of thepresent invention.

A laminated glass 11 illustrated in FIG. 6 includes an intermediate film1, a first component for laminated glass 21 and a second component forlaminated glass 22. The intermediate film 1 is interposed between thefirst component for laminated glass 21 and the second component forlaminated glass 22. The first component for laminated glass 21 islaminated on a first surface 1 a of the intermediate film 1. The secondcomponent for laminated glass 22 is laminated on a second surface thatis an opposite side of the first surface of the intermediate film 1. Thefirst component for laminated glass 21 is laminated on an outer surface3 a of the second layer 3. The second component for laminated glass 22is laminated on an outer surface 4 a of the third layer 4.

Accordingly, the laminated glass according to the present inventionincludes a first component for laminated glass, a second component forlaminated glass, and an intermediate film interposed between the firstcomponent for laminated glass and the second component for laminatedglass, and the intermediate film used is the intermediate film forlaminated glass according to the present invention.

Examples of the first component for laminated glass and the secondcomponent for laminated glass include glass plates and PET (polyethyleneterephthalate) films. The laminated glass covers not only a laminatedglass including an intermediate film interposed between two glassplates, but also a laminated glass including an intermediate filminterposed between a glass plate and a PET film or the like. Thelaminated glass is a laminate including a glass plate, and preferablyincludes at least one glass plate.

Examples of the glass plate include inorganic glass and organic glass.Examples of the inorganic glass include float plate glass,heat-absorbing plate glass, heat-reflective plate glass, polished plateglass, patterned glass, wired glass, linear-wired glass and green-tintedglass. The organic glass is synthetic resin glass used instead ofinorganic glass. Examples of the organic glass include polycarbonateplates and poly(meth)acrylic resin plates. Examples of thepoly(meth)acrylic resin plate include polymethyl (meth)acrylate plates.

The thickness of each of the first component for laminated glass and thesecond component for laminated glass is not particularly limited, and itis preferably within a range of 1 to 5 mm. In the case that thecomponent for laminated glass is a glass plate, the thickness of theglass plate is preferably within a range of 1 to 5 mm. In the case thatthe component for laminated glass is a PET film, the thickness of thePET film is preferably within a range of 0.03 to 0.5 mm.

The method for producing the laminated glass is not particularlylimited. For example, the intermediate film is sandwiched between thefirst component for laminated glass and the second component forlaminated glass, and then passed through a press roll or put into arubber bag and decompression-sucked, so that the air remained betweenthe first component for laminated glass or the second component forlaminated glass and the intermediate film is removed. Thereafter, theproduct is pre-bonded at about 70 to 110° C. so that a laminate isprovided. Next, the laminate is put into an autoclave or pressed so thatthe laminate is pressed at about 120 to 150° C. and a pressure of 1 to1.5 MPa, and thereby a laminated glass is obtained.

The laminated glass can be used for automobiles, railway carriages,aircrafts, ships, buildings, and the like. The laminated glass can alsobe used for other applications. The laminated glass is preferably alaminated glass for buildings or vehicles, and is more preferably alaminated glass for vehicles. The laminated glass can be suitably usedfor electric vehicles using electric motors and hybrid electric vehiclesusing internal-combustion engines and electric motors. The laminatedglass can be used for windshields, side glasses, rear glasses, and roofglasses of automobiles.

The following will describe the present invention in detail referringto, but not limited to, examples.

Synthesis Example 1 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 1

<Synthesis of Polyvinyl Butyral Resin>

To pure water (2890 g), a polyvinyl alcohol resin (191 g, degree ofpolymerization: 2500, degree of saponification: 79 mol %) was added andheated to be dissolved. The resulting solution was adjusted to atemperature of 12° C. A 35% by weight hydrochloric acid (201 g) andn-butyl aldehyde (150 g) were added thereto for deposition of apolyvinyl butyral resin. Then, the mixture was held at a temperature of50° C. for three hours for completion of the reaction. Unreacted n-butylaldehyde was washed away with excessive water, and the hydrochloric acidcatalyst was neutralized. The resulting product was dried after removalof salts, thereby giving a polyvinyl butyral resin. A degree ofacetylation of the obtained polyvinyl butyral resin was 21 mol %, adegree of butyralization thereof was 54 mol %, and a hydroxy groupcontent thereof was 25 mol %.

Synthesis Example 2 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 2

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 1700)having a degree of acetylation of 0.5 mol %, a degree of butyralizationof 64 mol %, and a hydroxy group content of 35.5 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 17.5 molarequivalents of acetic anhydride was added, and the mixture was stirredfor 300 minutes at a temperature of 80° C. After removal of pyridine,the polyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 1700) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 18 mol %, a degree of butyralization thereof was 64 mol %, anda hydroxy group content thereof was 18 mol %.

Synthesis Example 3 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 3

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 1700)having a degree of acetylation of 0.5 mol %, a degree of butyralizationof 64 mol %, and a hydroxy group content of 35.5 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 22.5 molarequivalents of acetic anhydride was added, and the mixture was stirredfor 300 minutes at a temperature of 80° C. After removal of pyridine,the polyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 1700) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 23 mol %, a degree of butyralization thereof was 64 mol %, anda hydroxy group content thereof was 13 mol %.

Synthesis Example 4 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 4

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 2300)having a degree of acetylation of 13 mol %, a degree of butyralizationof 59 mol %, and a hydroxy group content of 28 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 5 molar equivalentsof acetic anhydride was added, and the mixture was stirred for 300minutes at a temperature of 80° C. After removal of pyridine, thepolyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 2300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 23 mol %, a degree of butyralization thereof was 59 mol %, anda hydroxy group content thereof was 18 mol %.

Synthesis Example 5 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 5

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 1400)having a degree of acetylation of 6 mol %, a degree of butyralization of70 mol %, and a hydroxy group content of 24 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 6.8 molarequivalents of acetic anhydride was added, and the mixture was stirredfor 300 minutes at a temperature of 80° C. After removal of pyridine,the polyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 1400) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 12.8 mol %, a degree of butyralization thereof was 70 mol %,and a hydroxy group content thereof was 17.2 mol %.

Synthesis Example 6 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 6

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 1700)having a degree of acetylation of 0.5 mol %, a degree of butyralizationof 80 mol %, and a hydroxy group content of 19.5 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 6.5 molarequivalents of acetic anhydride was added, and the mixture was stirredfor 300 minutes at a temperature of 80° C. After removal of pyridine,the polyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 1700) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 7 mol %, a degree of butyralization thereof was 80 mol %, anda hydroxy group content thereof was 13 mol %.

Synthesis Example 7 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 7

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 1700)having a degree of acetylation of 1 mol %, a degree of butyralization of64 mol %, and a hydroxy group content of 35 mol % was dissolved intoluene. To 100 parts by weight of the polyvinyl butyral resin solution(toluene:polyvinyl butyral resin=95 parts by weight:5 parts by weight),6 parts by weight of trifluoroacetic acid was added, and the mixture wasstirred for 300 minutes at a temperature of 80° C. After removal oftoluene, the polyvinyl butyral resin was washed with water and dried, sothat a polyvinyl butyral resin (average degree of polymerization of1700) was obtained. A degree of acetylation of the obtained polyvinylbutyral resin was 1 mol %, a degree of butyralization thereof was 93 mol%, and a hydroxy group content thereof was 6 mol %.

Synthesis Example 8 Synthesis of Polyvinyl Acetal Resin Used inIntermediate Layers A of Comparative Examples 1 and 2

<Synthesis of Polyvinyl Butyral Resin>

To pure water (2890 g), a polyvinyl alcohol resin (191 g, degree ofpolymerization: 3000, degree of saponification: 87.2 mol %) was addedand heated to be dissolved. The resulting solution was adjusted to atemperature of 12° C. A 35% by weight hydrochloric acid (201 g) andn-butyl aldehyde (150 g) were added thereto for deposition of apolyvinyl butyral resin. Then, the mixture was held at a temperature of50° C. for five hours for completion of the reaction. Unreacted n-butylaldehyde was washed away with excessive water, and the hydrochloric acidcatalyst was neutralized. The resulting product was dried after removalof salts, thereby giving a polyvinyl butyral resin. A degree ofacetylation of the obtained polyvinyl butyral resin was 12.8 mol %, adegree of butyralization thereof was 63.5 mol %, and a hydroxy groupcontent thereof was 23.7 mol %.

Synthesis Example 9 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 8

<Synthesis of Polyvinyl Butyral Resin>

To pure water (2890 g), a polyvinyl alcohol resin (80 g, degree ofpolymerization: 2500, degree of saponification: 79 mol %) and apolyvinyl alcohol resin (111 g, degree of polymerization: 4000, degreeof saponification: 79 mol %) were added and heated to be dissolved. Theresulting solution was adjusted to a temperature of 12° C. A 35% byweight hydrochloric acid (201 g) and n-butyl aldehyde (150 g) were addedthereto for deposition of a polyvinyl butyral resin. Then, the mixturewas held at a temperature of 50° C. for three hours for completion ofthe reaction. Unreacted n-butyl aldehyde was washed away with excessivewater, and the hydrochloric acid catalyst was neutralized. The resultingproduct was dried after removal of salts, thereby giving a polyvinylbutyral resin. A degree of acetylation of the obtained polyvinyl butyralresin was 21 mol %, a degree of butyralization thereof was 54 mol %, anda hydroxy group content thereof was 25 mol %.

The proportion of a high molecular weight component X (polyvinyl butyralresin) having an absolute molecular weight of one million or more in theresulting polyvinyl butyral resin was 16.8%. The proportion of the highmolecular weight component Y (polyvinyl butyral resin) having amolecular weight y of one million or more in an obtained polyvinylbutyral resin Z was 19.2%.

Synthesis Example 10 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 9

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3200)having a degree of acetylation of 0.5 mol %, a degree of butyralizationof 64 mol %, and a hydroxy group content of 35.5 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 17.5 molarequivalents of acetic anhydride was added, and the mixture was stirredfor 300 minutes at a temperature of 80° C. After removal of pyridine,the polyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3200) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 18 mol %, a degree of butyralization thereof was 64 mol %, anda hydroxy group content thereof was 18 mol %.

Synthesis Example 11 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 10

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3200)having a degree of acetylation of 0.5 mol %, a degree of butyralizationof 64 mol %, and a hydroxy group content of 35.5 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 22.5 molarequivalents of acetic anhydride was added, and the mixture was stirredfor 300 minutes at a temperature of 80° C. After removal of pyridine,the polyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3200) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 23 mol %, a degree of butyralization thereof was 64 mol %, anda hydroxy group content thereof was 13 mol %.

Synthesis Example 12 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 11

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3500)having a degree of acetylation of 13 mol %, a degree of butyralizationof 59 mol %, and a hydroxy group content of 28 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 5 molar equivalentsof acetic anhydride was added, and the mixture was stirred for 300minutes at a temperature of 80° C. After removal of pyridine, thepolyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3500) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 23 mol %, a degree of butyralization thereof was 59 mol %, anda hydroxy group content thereof was 18 mol %.

Synthesis Example 13 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 12

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 6 mol %, a degree of butyralization of70 mol %, and a hydroxy group content of 24 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 6.8 molarequivalents of acetic anhydride was added, and the mixture was stirredfor 300 minutes at a temperature of 80° C. After removal of pyridine,the polyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 12.8 mol %, a degree of butyralization thereof was 70 mol %,and a hydroxy group content thereof was 17.2 mol %.

Synthesis Example 14 Synthesis of Polyvinyl Acetal Resin Used inIntermediate Layers A of Examples 13, 23, 26 to 29

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3200)having a degree of acetylation of 0.5 mol %, a degree of butyralizationof 80 mol %, and a hydroxy group content of 19.5 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 6.5 molarequivalents of acetic anhydride was added, and the mixture was stirredfor 300 minutes at a temperature of 80° C. After removal of pyridine,the polyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3200) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 7 mol %, a degree of butyralization thereof was 80 mol %, anda hydroxy group content thereof was 13 mol %.

Synthesis Example 15 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 14

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3200)having a degree of acetylation of 1 mol %, a degree of butyralization of64 mol %, and a hydroxy group content of 35 mol % was dissolved intoluene. To 100 parts by weight of the polyvinyl butyral resin solution(toluene:polyvinyl butyral resin=95 parts by weight:5 parts by weight),6 parts by weight of trifluoroacetic acid was added, and the mixture wasstirred for 300 minutes at a temperature of 80° C. After removal oftoluene, the polyvinyl butyral resin was washed with water and dried, sothat a polyvinyl butyral resin (average degree of polymerization of3200) was obtained. A degree of acetylation of the obtained polyvinylbutyral resin was 1 mol %, a degree of butyralization thereof was 93 mol%, and a hydroxy group content thereof was 6 mol %.

Synthesis Example 16 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 15

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 1 mol %, a degree of butyralization of83 mol %, and a hydroxy group content of 16 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 6 molar equivalentsof acetic anhydride was added, and the mixture was stirred for 300minutes at a temperature of 80° C. After removal of pyridine, thepolyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 7 mol %, a degree of butyralization thereof was 83 mol %, anda hydroxy group content thereof was 10 mol %.

Synthesis Example 17 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 16

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 1 mol %, a degree of butyralization of80 mol %, and a hydroxy group content of 19 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 11.8 molarequivalents of acetic anhydride was added, and the mixture was stirredfor 300 minutes at a temperature of 80° C. After removal of pyridine,the polyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 12.8 mol %, a degree of butyralization thereof was 80 mol %,and a hydroxy group content thereof was 7.2 mol %.

Synthesis Example 18 Synthesis of Polyvinyl Acetal Resin Used inIntermediate Layers A of Examples 17 and 24

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 1 mol %, a degree of butyralization of75 mol %, and a hydroxy group content of 24 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 11.8 molarequivalents of acetic anhydride was added, and the mixture was stirredfor 300 minutes at a temperature of 80° C. After removal of pyridine,the polyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 12.8 mol %, a degree of butyralization thereof was 75 mol %,and a hydroxy group content thereof was 12.2 mol %.

Synthesis Example 19 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 18

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 1 mol %, a degree of butyralization of60 mol %, and a hydroxy group content of 39 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 19.5 molarequivalents of acetic anhydride was added, and the mixture was stirredfor 300 minutes at a temperature of 80° C. After removal of pyridine,the polyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 20.5 mol %, a degree of butyralization thereof was 60 mol %,and a hydroxy group content thereof was 19.5 mol %.

Synthesis Example 20 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 19

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 1 mol %, a degree of butyralization of65 mol %, and a hydroxy group content of 34 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 19.5 molarequivalents of acetic anhydride was added, and the mixture was stirredfor 300 minutes at a temperature of 80° C. After removal of pyridine,the polyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 20.5 mol %, a degree of butyralization thereof was 65 mol %,and a hydroxy group content thereof was 14.5 mol %.

Synthesis Example 21 Synthesis of Polyvinyl Acetal Resin Used inIntermediate Layers A of Examples 20 and 25

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 1 mol %, a degree of butyralization of70 mol %, and a hydroxy group content of 29 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 19.5 molarequivalents of acetic anhydride was added, and the mixture was stirredfor 300 minutes at a temperature of 80° C. After removal of pyridine,the polyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 20.5 mol %, a degree of butyralization thereof was 70 mol %,and a hydroxy group content thereof was 9.5 mol %.

Synthesis Example 22 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 21

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 1 mol %, a degree of butyralization of60 mol %, and a hydroxy group content of 39 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 24 molar equivalentsof acetic anhydride was added, and the mixture was stirred for 300minutes at a temperature of 80° C. After removal of pyridine, thepolyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 25 mol %, a degree of butyralization thereof was 60 mol %, anda hydroxy group content thereof was 15 mol %.

Synthesis Example 23 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 22

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 1 mol %, a degree of butyralization of65 mol %, and a hydroxy group content of 34 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 24 molar equivalentsof acetic anhydride was added, and the mixture was stirred for 300minutes at a temperature of 80° C. After removal of pyridine, thepolyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 25 mol %, a degree of butyralization thereof was 65 mol %, anda hydroxy group content thereof was 10 mol %.

Synthesis Example 24 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 30

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 1 mol %, a degree of butyralization of65 mol %, and a hydroxy group content of 34 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 27 molar equivalentsof acetic anhydride was added, and the mixture was stirred for 300minutes at a temperature of 80° C. After removal of pyridine, thepolyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 28 mol %, a degree of butyralization thereof was 65 mol %, anda hydroxy group content thereof was 7 mol %.

Synthesis Example 25 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 31

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 1 mol %, a degree of butyralization of55 mol %, and a hydroxy group content of 44 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 27 molar equivalentsof acetic anhydride was added, and the mixture was stirred for 300minutes at a temperature of 80° C. After removal of pyridine, thepolyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 28 mol %, a degree of butyralization thereof was 55 mol %, anda hydroxy group content thereof was 17 mol %.

Synthesis Example 26 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 32

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 12 mol %, a degree of butyralizationof 45 mol %, and a hydroxy group content of 43 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 16 molar equivalentsof acetic anhydride was added, and the mixture was stirred for 300minutes at a temperature of 80° C. After removal of pyridine, thepolyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 28 mol %, a degree of butyralization thereof was 45 mol %, anda hydroxy group content thereof was 27 mol %.

Synthesis Example 27 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 33

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 12 mol %, a degree of butyralizationof 49 mol %, and a hydroxy group content of 39 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 13 molar equivalentsof acetic anhydride was added, and the mixture was stirred for 300minutes at a temperature of 80° C. After removal of pyridine, thepolyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 25 mol %, a degree of butyralization thereof was 49 mol %, anda hydroxy group content thereof was 26 mol %.

Synthesis Example 28 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 34

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 1 mol %, a degree of butyralization of91 mol %, and a hydroxy group content of 8 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 6 molar equivalentsof acetic anhydride was added, and the mixture was stirred for 300minutes at a temperature of 80° C. After removal of pyridine, thepolyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 7 mol %, a degree of butyralization thereof was 91 mol %, anda hydroxy group content thereof was 2 mol %.

Synthesis Example 29 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Example 35

<Synthesis of Polyvinyl Butyral Resin>

A polyvinyl butyral resin (average degree of polymerization of 3300)having a degree of acetylation of 1 mol %, a degree of butyralization of78 mol %, and a hydroxy group content of 21 mol % was dissolved inpyridine. To the dissolved polyvinyl butyral resin, 17 molar equivalentsof acetic anhydride was added, and the mixture was stirred for 300minutes at a temperature of 80° C. After removal of pyridine, thepolyvinyl butyral resin was washed with water and dried, so that apolyvinyl butyral resin (average degree of polymerization of 3300) wasobtained. A degree of acetylation of the obtained polyvinyl butyralresin was 18 mol %, a degree of butyralization thereof was 78 mol %, anda hydroxy group content thereof was 4 mol %.

Synthesis Example 30 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Comparative Example 3

<Synthesis of Polyvinyl Butyral Resin>

To pure water (2890 g), a polyvinyl alcohol resin (191 g, degree ofpolymerization: 2300, degree of saponification: 93 mol %) was added andheated to be dissolved. The resulting solution was adjusted to atemperature of 12° C. A 35% by weight hydrochloric acid (201 g) andn-butyl aldehyde (171 g) were added thereto for deposition of apolyvinyl butyral resin. Then, the mixture was held at a temperature of55° C. for five hours for completion of the reaction. Unreacted n-butylaldehyde was washed away with excessive water, and the hydrochloric acidcatalyst was neutralized. The resulting product was dried after removalof salts, thereby giving a polyvinyl butyral resin. A degree ofacetylation of the obtained polyvinyl butyral resin was 7 mol %, adegree of butyralization thereof was 72 mol %, and a hydroxy groupcontent thereof was 21 mol %.

Synthesis Example 31 Synthesis of Polyvinyl Acetal Resin Used in anIntermediate Layer A of Comparative Example 4

<Synthesis of Polyvinyl Butyral Resin>

To pure water (2890 g), a polyvinyl alcohol resin (191 g, degree ofpolymerization: 2300, degree of saponification: 99 mol %) was added andheated to be dissolved. The resulting solution was adjusted to atemperature of 12° C. A 35% by weight hydrochloric acid (201 g) andn-butyl aldehyde (190 g) were added thereto for deposition of apolyvinyl butyral resin. Then, the mixture was held at a temperature of55° C. for five hours for completion of the reaction. Unreacted n-butylaldehyde was washed away with excessive water, and the hydrochloric acidcatalyst was neutralized. The resulting product was dried after removalof salts, thereby giving a polyvinyl butyral resin. A acetylation of theobtained polyvinyl butyral resin was 1 mol %, a degree of butyralizationthereof was 79 mol %, and a hydroxy group content thereof was 20 mol %.

As a polyvinyl acetal resin used in protective layers B of Examples 1 to22, and 26 to 35 and Comparative Examples 1 to 4, a polyvinyl butyralresin (n-butyl aldehyde was used, degree of butyralization of 68.5 mol%, degree of acetylation of 1 mol %, hydroxy group content of 30.5 mol%) was prepared.

As a polyvinyl acetal resin used in protective layers B of Examples 23to 25, a polyvinyl butyral resin (n-butyl aldehyde was used, degree ofbutyralization of 70.5 mol %, degree of acetylation of 1.5 mol %,hydroxy group content of 28 mol %) was prepared.

The degrees of butyralization (degree of acetalization), degrees ofacetylation, and hydroxy group contents of the polyvinyl butyral resinsused in examples and comparative examples were measured by a method inconformity with ASTM D1396-92. It is to be noted that, in themeasurement in conformity with JIS K6728 “Testing methods for polyvinylbutyral”, the obtained numerical values were same as those obtained inthe measurement in conformity with ASTM D1396-92.

The following plasticizers were used in examples and comparativeexamples.

Triethylene glycol di-2-ethylhexanoate (3GO) (SP value: 9.06)

Triethylene glycol di-n-butanoate (3 GB) (SP value: 9.45)

Bis(2-(2-butoxyethoxyethyl)ester)hexanoate (EDENOL422) (SP value: 13.85)

Bis(2-butoxyethyl) adipate (D931) (SP value: 13.56)

Example 1 (1) Production of Intermediate Film

An amount of 100 parts by weight of a polyvinyl butyral resin (n-butylaldehyde was used, degree of butyralization of 54 mol %, degree ofacetylation of 21 mol %, hydroxy group content of 25 mol %) and 55 partsby weight of triethylene glycol di-2-ethyl hexanoate (3GO) as aplasticizer were sufficiently kneaded with a mixing roll to give acomposition for intermediate layer.

An amount of 100 parts by weight of a polyvinyl butyral resin (n-butylaldehyde was used, degree of butyralization of 68.5 mol %, degree ofacetylation of 1 mol %, hydroxy group content of 30.5 mol %) and 38.5parts by weight of triethylene glycol di-2-ethylhexanoate (3GO) as aplasticizer was sufficiently kneaded to give a composition forprotective layer.

The resulting composition for intermediate layer and the composition forprotective layer were molded using a co-extruder to give a multilayerintermediate film (810 μm in thickness) including a protective layer B(350 μm in thickness)/an intermediate layer A (110 μm in thickness)/aprotective layer B (350 μm in thickness).

(2) Production of Laminated Glass Used for Measurement of Loss Factor

The resulting multilayer intermediate film was cut into a piece in asize of 30 mm in length×320 mm in width. The multilayer intermediatefilm piece was sandwiched between two transparent float glass sheets (25mm in length×305 mm in width×2.0 mm in thickness) and held in a vacuumlaminator at 90° C. for 30 minutes to be vacuum-pressed, thereby givinga laminate. In the laminate, a multilayer intermediate film partprotruding from the glass sheets was cut. In this manner, a laminatedglass to be used for measurement of loss factor was prepared.

(3) Production of Laminated Glass Used for Bubble Formation Test A andBubble Formation Test B

The resulting multilayer intermediate film was cut into a piece in asize of 30 cm in length×15 cm in width and stored at a temperature of23° C. for 10 hours. It is to be noted that the faces of the resultingmultilayer intermediate film was embossed, and ten point height of theembossment was 30 μm. In the cut multilayer intermediate film piece,four through holes with a diameter of 6 mm were formed at intersectionsof lines drawn in the lengthwise direction at positions of 8 cm insidefrom edges of the multilayer intermediate film and lines drawn in thecrosswise direction at position of 5 cm inside from edges of themultilayer intermediate film.

The multilayer intermediate film with through holes were sandwichedbetween two transparent float glass sheets (30 cm in length×15 cm inwidth×2.5 mm in thickness) to give a laminate. A width of 2 cm of theperipheral edge of the laminate was heat-sealed, and thereby the airremained in the embossment and the air remained in the through holeswere sealed. This laminate was press-bonded at 135° C. and 1.2 MPa for20 minutes, and thereby the residual air was dissolved into themultilayer intermediate film. As a result, a laminated glass to be usedin the bubble formation test A and the bubble formation test B wasobtained.

Examples 2 to 35 and Comparative Examples 1 to 4

Except that the types and amounts of the polyvinyl acetal resin and theplasticizer used in the intermediate layer A and the protective layersB, and the thicknesses of the intermediate layer A and the protectivelayers B were set as shown in Tables 1 to 5, a multilayer intermediatefilm and a laminated glass were obtained in the same manner as inExample 1. The polyvinyl butyral resins used in Examples 2 to 35 andComparative Examples 1 to 4 each were a resin prepared by butyralizationof n-butyl aldehyde.

(Evaluations)

(1) A Peak Temperature of Tan δ which Appears at the Lowest Temperature,and a Maximum Value of Tan δ at a Peak which Appears at the LowestTemperature

The resulting intermediate films were stored at a temperature of 20° C.for a month. The intermediate films were each cut into a circle with adiameter of 8 mm and examined for the dispersion of dynamicviscoelasticity with temperatures at a rate of temperature rise of 5°C./min under the conditions of at a distortion of 1.0% and a frequencyof 1 Hz by a shearing method using a viscoelasticity measuring device(“ARES” from Rheometric Scientific Inc.). In this manner, a peaktemperature of tan δ which appears at the lowest temperature, and amaximum value of tan δ at a peak which appears at the lowest temperaturewere measured.

(2) Loss Factor

Laminated glasses to be used for the measurement of loss factor werestored at 20° C. for a month. The loss factor of each stored laminatedglass was measured at 20° C. by a center exciting method using ameasurement device “SA-01” (RION Co., Ltd.). Based on the obtained lossfactors, loss factors (20° C. loss factor) in the fourth mode (around3150 Hz) of resonance frequencies were evaluated.

(3) Bubble Formation Test a (State of Bubble Formation)

With respect to each of the multilayer intermediate films, fivelaminated glasses to be used in the bubble formation test A wereproduced, and then left to stand for 100 hours in a 50° C. oven. Theleft laminated glasses were visually examined for the presence of bubbleformation and the size of the bubbles in a plan view, and the state ofbubble formation was evaluated based on the following criteria.

[Criteria for the State of Bubble Formation in the Bubble Formation TestA]

The bubbles generated in the five laminated glasses were eachapproximated to an ellipse, and the area of the ellipse was defined asthe bubble formation area. The areas of the ellipses observed in thefive laminated glass were averaged, and the proportion (percentage) ofthe averaged value (bubble formation area) of the areas of the ellipsesto the area (30 cm×15 cm) of the laminated glass was determined.

◯◯: No bubbles were observed in any of five laminated glasses

◯: The ratio of the average value (bubble formation area) of the areasof the ellipses was lower than 5%

Δ: The ratio of the average value (bubble formation area) of the areasof the ellipses was 5% or higher and lower than 10%

X: The ratio of the average value (bubble formation area) of the areasof the ellipses was 10% or higher

(4) Bubble Formation Test B (State of Bubble Formation)

With respect to each of the multilayer intermediate films, laminatedglasses to be used in the bubble formation test B were produced, andthen left to stand for 24 hours in a 50° C. oven. The number oflaminated glass in which bubble formation was visually observed amongthe left laminated glasses was counted, and the state of bubbleformation was evaluated based on the following criteria.

[Criteria for the State of Bubble Formation in the Bubble Formation TestB]

◯◯: The number of laminated glasses in which bubbles were visuallyobserved was 5 or less

◯: The number of laminated glasses in which bubbles were visuallyobserved was not less than 6 but not more than 10

Δ: The number of laminated glasses in which bubbles were visuallyobserved was not less than 11 but not more than 15

X: The number of laminated glasses in which bubbles were visuallyobserved was 16 or more

(5) Measurement of Elastic Modulus G′ by Test Method A

An amount of 100 parts by weight of each of the polyvinyl acetal resins(polyvinyl acetal resins used in the first layers) which is contained inthe first layers of the intermediate films for laminated glass ofexamples and comparative examples and 60 parts by weight of triethyleneglycol di-2-ethylhexanoate (3GO) as a plasticizer were sufficientlykneaded to give a kneaded product. The resulting kneaded products wereeach press-molded to be formed into resin films A having an averagethickness of 0.35 mm. The obtained resin films A were left to standunder the conditions of a temperature of 25° C. and a relative humidityof 30% for two hours. After standing for two hours, the viscoelasticitywas measured using ARES-G2 (TA INSTRUMENTS). The geometry used here wasa 8-mm-diameter parallel plate. The measurement was performed under thecondition wherein the temperature was lowered from 100° C. to −10° C. ata lowering rate of 3° C./min at a frequency of 1 Hz and a distortion of1%. In the obtained measurement results, the peak temperature of theloss factor was defined as a glass transition temperature Tg (° C.).Further, based on the measurement results and the glass transitiontemperature Tg, the value of the elastic modulus G′(Tg+30) at (Tg+30)°C. and the value of the elastic modulus G′(Tg+80) at (Tg+80)° C. wereobtained. In addition, the ratio (G′(Tg+80)/G′(Tg+30)) was determined.

(6) Measurement of Elastic Modulus G′ by Test Method B

The intermediate film for laminated glass of each of the examples andcomparative examples was stored in a constant temperature and humidityroom (humidity: 30% (±3%), temperature: 23° C.) for a month. Immediatelyafter the storage for a month, the surface layer, the intermediatelayer, and the surface layer were separated, and thereby theintermediate layer was taken out. One gram of the separated intermediatelayer was placed in a mold (2 cm in length×2 cm in width×0.76 mm inthickness) disposed between two polyethylene terephthalate (PET) films.The intermediate layer was preheated at a temperature of 150° C. and apressure of 0 kg/cm² for 10 minutes, and then press-molded at 80 kg/cm²for 15 minutes. The press-molded intermediate layer was placed in a handpress machine set to 20° C. in advance, and then pressed at 10 MPa for10 minutes. Thereby, the intermediate layer was cooled down. Next, oneof the two PET films was peeled off from the mold disposed therebetween,and the intermediate layer in the mold was stored in a constanttemperature and humidity room (humidity: 30% (±3%), temperature: 23° C.)for 24 hours. Then, the viscoelasticity of the intermediate layer wasmeasured using ARES-G2 (TA INSTRUMENTS). The geometry used here was a8-mm-diameter parallel plate. The measurement was performed under thecondition wherein the temperature was lowered from 100° C. to −10° C. ata lowering rate of 3° C./min and at a frequency of 1 Hz and a distortionof 1%. In the obtained measurement results, the peak temperature of theloss factor was defined as a glass transition temperature Tg (° C.).Further, based on the measurement results and the glass transitiontemperature Tg, the value of the elastic modulus G′(Tg+30) at (Tg+30)°C. and the value of the elastic modulus G′(Tg+80) at (Tg+80)° C. wereobtained. In addition, the ratio (G′(Tg+80)/G′(Tg+30)) was determined.

(7) Measurement of Absolute Molecular Weight and Molecular Weight y

(Measurement of Absolute Molecular Weight)

The absolute molecular weight and molecular weight in terms ofpolystyrene for obtaining the proportions of the high molecular weightcomponent X and the high molecular weight component Y in SynthesisExample 9 are values obtained by separating the surface layers and theintermediate layer of each resulting multilayer intermediate film andfollowing the below procedures.

For measurement of the absolute molecular weight, each multilayerintermediate film was left to stand in a constant temperature andhumidity room (humidity of 30% (±3%), temperature of 23° C.) for amonth. After standing for a month, the multilayer intermediate film wasseparated into the surface layers and the intermediate layer. The peeledintermediate layer was dissolved in tetrahydrofuran (THF), therebypreparing a 0.1% by weight solution. The resulting solution was analyzedusing a Gel Permeation Chromatography (GPC) device (HitachiHigh-Technologies Corp., “RI: L2490, auto sampler: L-2200, pump: L-2130,column oven: L-2350, Column: GL-A120-S and GL-A100MX-S in series”). TheGPC device is connected with a light scattering detector for GPC(VISCOTEK, “Model 270 (RALS+VISCO)”), enabling analysis of achromatogram by each detector. Peaks of polyvinyl acetal resincomponents in chromatograms by an RI detector and an RALS detector wereanalyzed using analysis software (OmniSEC). In this manner, the absolutemolecular weight at each elution time of the polyvinyl acetal resin wasobtained. The proportion of an area where the absolute molecular weightof the polyvinyl acetal resin is one million or more in the peak area ofthe polyvinyl acetal resin detected by the RI detector was expressed inpercentage (%).

Each peak in a chromatogram satisfies the following equations.A _(RI) =c×(dn/dc)×K _(RI)  formula (1)A _(RALS) =c×M×(dn/dc)² ×K _(RALS)  formula (2)

Here, c represents polymer concentration in the solution, (dn/dc)represents a refractive index increment, M represents an absolutemolecular weight, and K represents a system's coefficient.

In a specific procedure of measurement, a polystyrene standard sample(VISCOTEK, PolyCAL (registered trade mark), TDS-PS-NB, Mw=98390,dn/dc=0.185) having known c, M, and (dn/dc) was used to prepare 0.1% byweight solution in THF. Based on the GPC measurement result of theprepared polystyrene solution, the system's coefficient of each detectorwas obtained using the formula (1) and the formula (2).

Next, the peeled intermediate layer was dissolved in THF to prepare asolution in THF. Based on the GPC measurement result of the obtainedpolyvinyl acetal resin solution, the absolute molecular weight M of thepolyvinyl acetal resin was obtained using the formula (1) and theformula (2).

For analysis of the intermediate layer (including the polyvinyl acetalresin and the plasticizer), the concentration of the polyvinyl acetalresin in the polyvinyl acetal resin solution needs to be determined. Theconcentration of the polyvinyl acetal resin is calculated based on themeasurement result of the plasticizer content.

Measurement of Plasticizer Content:

The plasticizer was dissolved in THF to prepare plasticizer-THFsolutions having plasticizer contents of 10% by weight, 15% by weight,20% by weight, 25% by weight, 30% by weight, 35% by weight, 40% byweight, 45% by weight, and 50% by weight. Each obtained plasticizer-THFsolution was subjected to GPC measurement and the peak area of theplasticizer was obtained. The peak areas relative to concentrations ofthe plasticizer were plotted, so that an approximate straight line wasobtained. Then, the solution in THF which contains the intermediatelayer dissolved in THF was subjected to GPC measurement. The plasticizercontent was obtained from the peak area of the plasticizer using theapproximate straight line.

(Measurement of Molecular Weight y)

In the same manner as in the measurement method of the absolutemolecular weight, the proportion (%) of the high molecular weightcomponent Y having a molecular weight y of one million or more in thepolyvinyl acetal resin was calculated based on the proportion of thearea corresponding to the region where the molecular weight is onemillion or more in the peak area (measurement result of GPC) detected bythe RI detector in measurement of the molecular weight in terms ofpolystyrene by gel permeation chromatography (GPC).

In order to measure the molecular weight in terms of polystyrene,polystyrene standard samples with known molecular weights were subjectedto GPC measurement. The polystyrene standard samples used (SHOWA DENKOK.K., “Shodex Standard SM-105”, “Shodex Standard SH-75”) were 14 sampleswith the respective weight average molecular weights of 580, 1,260,2,960, 5,000, 10,100, 21,000, 28,500, 76,600, 196,000, 630,000,1,130,000, 2,190,000, 3,150,000, and 3,900,000. The weight averagemolecular weights relative to the elution times indicated by the peaktops of the standard sample peaks are plotted so that an approximatestraight line was drawn. The obtained approximate straight line was usedas a calibration curve. A multilayer intermediate film was left in aconstant temperature and humidity room (humidity: 30% (±3%),temperature: 23° C.) for one month, and then the surface layers and theintermediate layer were separated. The separated intermediate layer wasdissolved in tetrahydrofuran (THF) to prepare a 0.1% by weight solution.The obtained solution was analyzed using a GPC device, and thereby thepeak area of the polyvinyl acetal resin in the intermediate layer wasmeasured. Based on the elution time of the polyvinyl acetal resin in theintermediate layer and the calibration curve, the area corresponding toa region where the molecular weight in terms of polystyrene of thepolyvinyl acetal resin in the intermediate layer was one million or morewas calculated. The area corresponding to the region where the molecularweight in terms of polystyrene of the polyvinyl acetal resin in theintermediate layer was one million or more was divided by the peak areaof the polyvinyl acetal resin in the intermediate layer, and theobtained value was expressed in a percentage (%). Thereby, theproportion (%) of the high molecular weight component Y having amolecular weight y of one million or more in the polyvinyl acetal resinwas calculated.

Tables 1 to 5 show the results. In Tables 1 to 5, 3GO indicatestriethylene glycol di-2-ethylhexanoate.

TABLE 1 Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 1Intermediate Resin Degree of butyralization 54 64 64 59 70 80 93 63.5layer A (mol %) Degree of acetylation (mol %) 21 18 23 23 12.8 7 1 12.8Hydroxy group content 25 18 13 18 17.2 13 6 23.7 (mol %) Amount (partsby weight) 100 100 100 100 100 100 100 100 Plasticizer Kind 3GO 3GO 3GO3GO 3GO 3GO 3GO 3GO Amount (part by weight) 55 55 45 50 55 55 55 60Protective Resin Degree of butyralization 68.5 68.5 68.5 68.5 68.5 68.568.5 68.5 layer B (mol %) Degree of acetylation (mol %) 1 1 1 1 1 1 1 1Hydroxy group content 30.5 30.5 30.5 30.5 30.5 30.5 30.5 30.5 (mol %)Amount (parts by weight) 100 100 100 100 100 100 100 100 PlasticizerKind 3GO 3GO 3GO 3GO 3GO 3GO 3GO 3GO Amount (parts by weight) 38.5 38.538.5 38.5 38.5 38.5 38.5 38.5 Film composition B/A/B B/A/B B/A/B B/A/BB/A/B B/A/B B/A/B B/A/B Thickness of protective layer B (μm)/thicknessof 350/110/ 350/110/ 350/110/ 350/80/ 350/110/ 350/110/ 350/300/350/110/ intermediate layer A (μm)/thickness of 350 350 350 350 350 350350 350 protective layer B (μm) Thickness of intermediate layer A(μm)/total thickness 0.16 0.16 0.16 0.11 0.16 0.16 0.43 0.16 ofprotective layers B (μm) Peak temperature (° C.) of tan δ which appears−2.4 −4 −3.1 −3.4 −2.3 −1.8 −4.5 −4.2 at the lowest temperature Maximumvalue of tan δ at a neak which appears 1.3 1.32 1.54 1.41 1.32 1.31 1.411.05 at the lowest temperature 20° C. loss factor at around 3150 Hz 0.330.33 0.45 0.35 0.33 0.32 0.35 0.28

TABLE 2 Comp. Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 2Intermediate Resin Degree of butyralization 54 64 64 59 70 80 93 63.5layer A (mol %) Degree of acetylation 21 18 23 23 12.8 7 1 12.8 (mol %)Hydroxy group content 25 18 13 18 17.2 13 6 23.7 (mol %) Amount (partsby weight) 100 100 100 100 100 100 100 100 Plasticizer Kind 3GO 3GO 3GO3GO 3GO 3GO 3GO 3GO Amount (part by weight) 60 60 60 60 60 60 60 60Protective Resin Degree of butyralization 68.5 68.5 68.5 68.5 68.5 68.568.5 68.5 layer B (mol %) Degree of acetylation 1 1 1 1 1 1 1 1 (mol %)Hydroxy group content 30.5 30.5 30.5 30.5 30.5 30.5 30.5 30.5 (mol %)Amount (parts by weight) 100 100 100 100 100 100 100 100 PlasticizerKind 3GO 3GO 3GO 3GO 3GO 3GO 3GO 3GO Amount (parts by weight) 34 33.5 3132 35.5 32.5 31.5 38.5 Film composition B/A/B B/A/B B/A/B B/A/B B/A/BB/A/B B/A/B B/A/B Thickness of protective layer B (μm)/thickness of350/110/ 350/110/ 350/110/ 350/80/ 350/110/ 350/110/ 350/300/ 350/110/intermediate layer A (μm)/thickness of protective 350 350 350 350 350350 350 350 layer B (μm) Thickness of intermediate layer A (μm)/total0.16 0.16 0.16 0.11 0.16 0.16 0.43 0.16 thickness of protective layers B(μm) Peak temperature (° C.) of tan δ which appears −0.85 −4 −3.1 −3.4−2.3 −1.8 −4.5 −4.2 at the lowest temperature Maximum value of tan δ ata neak which appears at 1.3 1.32 1.54 1.41 1.32 1.31 1.41 1.05 thelowest temperature 20° C. loss factor at around 3150 Hz 0.33 0.33 0.450.35 0.33 0.32 0.35 0.28 Bubble formation test A (state of bubbleformation) ◯◯ ◯◯ ◯◯ ◯◯ ◯◯ ◯◯ ◯◯ X Bubble formation test B (state ofbubble formation) ◯ ◯ ◯ ◯ ◯ ◯ ◯ X Test method A: Glass transitiontemperature −2.4 −4.3 −3.7 −4 −2.9 −2.6 −5.1 −2.3 (Tg) (° C.) Testmethod A: G′(Tg + 30) (Pa) 230800 222100 223300 224600 231200 231500213200 234500 Test method A: G′(Tg + 80) (Pa) 155000 147000 149300 16200153400 157400 147500 142000 Test method A: G′(Tg + 80)/G′(Tg + 30) 0.670.66 0.67 0.68 0.86 0.68 0.69 0.61 Test method B: Glass transitiontemperature −4.21 −6.04 −6.01 −5.21 −5.22 −5.23 −6.77 −4.11 (Tg) (° C.)Test method B: G′(Tg + 30) (Pa) 210300 208500 205500 197800 205200205600 181000 224500 Test method B: G′(Tg + 80) (Pa) 139500 137500137400 134000 135800 136400 128600 131000 Test method B: G′(Tg +80)/G′(Tg + 30) 0.66 0.66 0.87 0.68 0.66 0.66 0.68 0.58

TABLE 3 Ex. 15 Ex. 16 Ex. 17 Ex. 18 Ex. 19 Ex. 20 Intermediate ResinDegree of butyralization (mol %) 83 80 75 60 65 70 layer A Degree ofacetylation (mol %) 7 12.8 12.8 20.5 20.5 20.5 Hydroxy group content(mol %) 10 7.2 12.2 19.5 14.5 9.5 Amount (parts by weight) 100 100 100100 100 100 Plasticizer Kind 3GO 3GO 3GO 3GO 3GO 3GO Amount (parts byweight) 60 60 60 60 60 60 Protective Resin Degree of butyralization (mol%) 68.5 68.5 68.5 68.5 68.5 68.5 layer B Degree of acetylation (mol %) 11 1 1 1 1 Hydroxy group content (mol %) 30.5 30.5 30.5 30.5 30.5 30.5Amount (parts by weight) 100 100 100 100 100 100 Plasticizer Kind 3GO3GO 3GO 3GO 3GO 3GO Amount (parts by weight) 31.5 30 32 32 31 30 Filmcomposition B/A/B B/A/B B/A/B B/A/B B/A/B B/A/B Thickness of protectivelayer B (μm)/thickness 350/110/350 350/110/350 350/110/350 350/110/350350/110/350 350/110/350 of intermediate layer A (μm)/thickness ofprotective layer B (μm) Thickness of intermediate layer A (μm/total 0.160.16 0.16 0.16 0.16 0.16 thickness of protective layers B (μm) Peaktemperature (° C.) of tan δ which appears at the −2.8 −4 −3.5 −3.4 −4.6−3.9 lowest temperature Maximum value of tan δ at a neak which appearsat the 1.36 1.41 1.37 1.33 1.36 1.43 lowest temperature 20° C. lossfactor at around 3510 Hz 0.34 0.35 0.34 0.33 0.34 0.37 Bubble formationtest A (state of bubble formation) ◯◯ ◯◯ ◯◯ ◯◯ ◯◯ ◯◯ Bubble formationtest B (state of bubble formation) ◯ ◯ ◯ ◯ ◯ ◯ Test method A: Glasstransition temperature (Tg) (° C.) −3.1 −5.1 −3.2 −3.2 −4.7 −5.8 Testmethod A: G′(Tg + 30) (Pa) 221200 204500 229200 231200 213200 208500Test method A: G′(Tg + 80) (Pa) 149400 140200 160000 161300 149400139200 Test method A: G′(Tg + 80)/G′(Tg + 30) 0.38 0.69 0.70 0.70 0.700.67 Test method B: Glass transition temperature (Tg) (° C.) −3.4 −4.8−4.2 −4 −5.5 −4.5 Test method B: G′(Tg + 30) (Pa) 221500 206500 201600228800 208500 180400 Test method B: G′(Tg + 80) (Pa) 149000 140800137400 156800 141600 120800 Test method B: G′(Tg + 80)/G′(Tg + 30) 0.570.68 0.58 0.69 0.68 0.67

TABLE 4 Ex. 21 Ex. 22 Ex. 23 Ex. 24 Ex. 25 Ex. 26 Ex. 27 Ex. 28 Ex. 29Inter- Resin Degree of 80 65 80 75 70 80 80 80 80 mediate butyralizationlayer A (mol %) Degree of 25 25 7 12.8 20.5 7 7 7 7 acetylation (mol %)Hydroxy group 15 10 13 12.2 9.5 13 13 13 13 content (mol %) Amount(parts 100 100 100 100 100 100 100 100 100 by weight) Plasticizer Kind3GO 3GO 3GO 3GO 3GO 3GB EDENOL D931 DBA 422 Amount (parts 60 60 80 80 8050 50 50 50 by weight) Protective Resin Degree of 88.5 68.5 70.5 70.570.5 68.5 88.5 88.5 88.5 layer B butyralization (mol %) Degree of 1 11.5 1.5 1.5 1 1 1 1 acetylation (mol %) Hydroxy group 30.5 30.5 28 28 2830.5 30.5 30.5 30.5 content (mol %) Amount (parts 100 100 100 100 100100 100 100 100 by weight) Plasticizer Kind 3GO 3GO 3GO 3GO 3GO 3GO 3GO3GO 3GO Amount (parts 29.5 27.5 34.5 34 32 28 31 31 28 by weight) Filmcomposition B/A/B B/A/B B/A/B B/A/B B/A/B B/A/B B/A/B B/A/B B/A/BThickness of protective layer B(μm)/ 350/110/ 350/110/ 350/110/ 350/110/350/110/ 3GB EDENCL D931 OBA thickness of protective layer B (μm) 350350 350 350 350 422 Thickness of intermediate layer A (μm/ 0.16 0.160.18 0.16 0.16 0.16 0.16 0.16 0.16 total thickness of protective layersB(μm) Peak temperature (° C.) of tan δ which −4.6 −4.4 −4.8 −5.2 −4.3−5.8 −3.6 −4.2 −5.5 appears at the lowest temperature Maximum value oftan δ at a peak which 1.46 1.5 1.31 1.43 1.45 1.51 1.48 1.47 1.5 appearsat the lowest temperature 20° C. loss factor at around 3150 Hz 0.35 0.410.32 0.35 0.38 0.42 0.38 0.39 0.42 Bubble formation test A (state ofbubble ◯◯ ◯◯ ◯◯ ◯◯ ◯◯ ◯◯ ◯◯ ◯◯ ◯◯ formation) Bubble formation test B(state of bubble ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ formation) Test method A: Glasstransition −4.1 −5.6 −2.6 −3.2 −5.8 −8.54 −5.6 −6.1 −7.9 temperature(Tg) (° C.) Test method A: G′(Tg + 30) (Pa) 212400 203900 231500 229200206500 198500 214600 212500 204500 Test method A: G′(Tg + 80) (Pa)144600 139600 157400 160000 139200 136000 145300 144800 139200 Testmethod A: G′(Tg + 80)/G′(Tg + 30) 0.88 0.68 0.68 0.70 0.67 0.69 0.680.68 0.68 Test method B: Glass transition −5.1 −5.3 −5.7 −5.9 −4.8 −5.3−4.4 −5 −8.3 temperature (Tg) (° C.) Test method B: G′(Tg + 30) (Pa)209100 203000 202600 201600 180400 202000 213900 211000 205600 Testmethod B: G′(Tg + 80) (Pa) 140800 138700 135400 137400 121000 137200145500 140500 140200 Test method B: G′(Tg + 80)/G′(Tg + 30) 0.67 0.680.67 0.68 0.67 0.68 0.68 0.67 0.68

TABLE 5 Comp. Comp. Ex. 30 Ex. 31 Ex. 32 Ex. 33 Ex. 34 Ex. 35 Ex. 3 Ex.4 Intermediate Resin Degree of butyralization 85 55 45 49 91 78 72 73layer A (mol %) Degree of acetylation 28 28 28 28 7 18 7 1 (mol %)Hydroxy group content 7 17 27 26 2 4 21 20 (mol %) Amount (parts byweight) 100 100 100 100 100 100 100 100 Plasticizer Kind 3GO 3GO 3GO 3GO3GO 3GO 3GO 3GO Amount (parts by weight) 60 60 60 60 60 60 60 60Protective Resin Degree of butyralization 68.5 68.5 68.5 68.5 68.5 68.568.5 68.5 layer B (mol %) Degree of acetylation 1 1 1 1 1 1 1 1 (mol %)Hydroxy group content 30.5 30.5 30.5 30.5 30.5 30.5 30.5 30.5 (mol %)Amount (parts by weight) 100 100 100 100 100 100 100 100 PlasticizerKind 3GO 3GO 3GO 3GO 3GO 3GO 3GO 3GO Amount (parts by weight) 27 28 38.538.5 30 27 38.5 38.5 Film composition B/A/B B/A/B B/A/B B/A/B B/A/BB/A/B B/A/B B/A/B Thickness of protective layer B (μm)/thickness of350/110/ 350/110/ 350/110/ 350/110/ 350/110/ 350/110/ 350/110/ 350/110/intermediate layer A (μm)/thickness 350 350 350 350 350 350 350 350 ofprotective layer B(μm) Thickness of intermediate layer A (μm/totalthickness 0.16 0.16 0.16 0.16 0.16 0.16 0.16 0.16 of protective layersB(μm) Peak temperature (° C.) of tan δ which appears −4.8 −5.1 −3.6 −3.2−5.1 −5.4 −3.6 −3.1 at the lowest temperature Maximum value of tan δ ata peak which appears 1.44 1.39 1.31 1.3 1.46 1.47 0.98 1.03 at thelowest temperature 20° C. loss factor at around 3150 Hz 0.37 0.36 0.330.33 0.38 0.39 0.26 0.27 Bubble formation test A (state of bubbleformation) ◯◯ ◯◯ ◯◯ ◯◯ ◯◯ ◯◯ — — Bubble formation test B (state ofbubble formation) ◯ ◯ ◯ ◯ ◯ ◯ — — Test method A: Glass transition −6.9−7.8 −1.6 −2.2 −6.3 −7.2 — — temperature (Tg) (° C.) Test method A:G′(Tg + 30) (Pa) 207600 212400 236800 232900 209500 211200 — — Testmethod A: G′(Tg + 80) (Pa) 141600 143200 164000 161700 139600 140900 — —Test method A: G′(Tg + 80)/G′(Tg + 30) 0.38 0.67 0.69 0.69 0.67 0.67 — —Test method B: Glass transition −5.3 −5.5 −4.2 −3.7 −5.6 −8 — —temperature (Tg) (° C.) Test method B: G′(Tg + 30) (Pa) 210400 215700228500 224900 210200 214500 — — Test method B: G′(Tg + 80) (Pa) 142300144500 155300 152600 140100 143000 — — Test method B: G′(Tg +80)/G′(Tg + 30) 0.88 0.67 0.68 0.68 0.67 0.67 — —

FIG. 7 is a phase diagram of three values including a degree ofacetalization, a degree of acetylation, and a hydroxy group content of apolyvinyl acetal resin contained in the first layer of each of theintermediate films for laminated glass of Examples 1 to 7 andComparative Example 1, and indicates values of the degree ofacetalization, the degree of acetylation, and the hydroxy group content.

FIG. 8 is a phase diagram of three values including a degree ofacetalization, a degree of acetylation, and a hydroxy group content of apolyvinyl acetal resin contained in the first layer of each of theintermediate films for laminated glass of Examples 8 to 14 andComparative Example 2, and indicates values of the degree ofacetalization, the degree of acetylation, and the hydroxy group content.

FIG. 9 is a phase diagram of three values including a degree ofacetalization, a degree of acetylation, and a hydroxy group content of apolyvinyl acetal resin contained in the first layer of each of theintermediate films for laminated glass of Examples 15 to 35 andComparative Examples 3 and 4, and indicates values of the degree ofacetalization, the degree of acetylation, and the hydroxy group content.

In the intermediate films for laminated glass of the examples andcomparative examples (except for Comparative Examples 3 and 4), theelastic modulus G′ of resin films B (first layers) that containplasticizers of the first layer and plasticizers of the first layer inamounts as shown in Tables 2 to 5 was measured after migration of theplasticizer among layers of the multilayer intermediate film. As aresult as shown in Table 2 to 5, the ratio (G′(Tg+80)/G′(Tg+30)) of theresin film B was similar to the ratio (G′(Tg+80)/G′(Tg+30)) of a resinfilm A containing 100 parts by weight of the polyvinyl acetal resin inthe first layer and 60 parts by weight of 3GO.

EXPLANATION OF SYMBOLS

-   1 Intermediate film-   1 a First surface-   1 b Second surface-   2 First layer-   2 a First surface-   2 b Second surface-   3 Second layer-   3 a Outer surface-   4 Third layer-   4 a Outer surface-   11 Laminated glass-   21 First component for laminated glass-   22 Second component for laminated glass

The invention claimed is:
 1. An intermediate film for laminated glass having a layered structure including at least two layers, comprising: a first layer containing a polyvinyl acetal resin and a plasticizer; and a second layer positioned on a first surface of the first layer, wherein, in a phase diagram of three values including a degree of acetalization, a degree of acetylation, and a hydroxy group content of the polyvinyl acetal resin contained in the first layer, the values of the degree of acetalization, the degree of acetylation, and the hydroxy group content each fall within a region surrounded by a line including four straight lines connecting a first coordinate (degree of acetalization:degree of acetylation:hydroxy group content=70 mol %:30 mol %:0 mol %), a second coordinate (degree of acetalization:degree of acetylation:hydroxy group content=34 mol %:30 mol %:36 mol %), a third coordinate (degree of acetalization:degree of acetylation:hydroxy group content=94 mol %:0 mol %:6 mol %), and a fourth coordinate (degree of acetalization:degree of acetylation:hydroxy group content=100 mol %:0 mol %:0 mol %) in the stated order.
 2. The intermediate film for laminated glass according to claim 1, wherein, in the phase diagram of three values including a degree of acetalization, a degree of acetylation, and a hydroxy group content of the polyvinyl acetal resin contained in the first layer, the values of the degree of acetalization, the degree of acetylation, and the hydroxy group content each fall within a region surrounded by a line including four straight lines connecting the first coordinate (degree of acetalization:degree of acetylation:hydroxy group content=70 mol %:30 mol %:0 mol %), the second coordinate (degree of acetalization:degree of acetylation:hydroxy group content=34 mol %:30 mol %:36 mol %), a fifth coordinate (degree of acetalization:degree of acetylation:hydroxy group content=95 mol %:0 mol %:5 mol %), and the fourth coordinate (degree of acetalization:degree of acetylation:hydroxy group content=100 mol %:0 mol %:0 mol %) in the stated order.
 3. The intermediate film for laminated glass according to claim 1, wherein, in the phase diagram of three values including a degree of acetalization, a degree of acetylation, and a hydroxy group content of the polyvinyl acetal resin contained in the first layer, the values of the degree of acetalization, the degree of acetylation, and the hydroxy group content each fall within a region surrounded by a line including four straight lines connecting the first coordinate (degree of acetalization:degree of acetylation:hydroxy group content=70 mol %:30 mol %:0 mol %), the second coordinate (degree of acetalization:degree of acetylation:hydroxy group content=34 mol %:30 mol %:36 mol %), the third coordinate (degree of acetalization:degree of acetylation:hydroxy group content=94 mol %:0 mol %:6 mol %), and a sixth coordinate (degree of acetalization:degree of acetylation:hydroxy group content=95 mol %:5 mol %:0 mol %) in the stated order.
 4. The intermediate film for laminated glass according to claim 1, wherein, in the phase diagram of three values including a degree of acetalization, a degree of acetylation, and a hydroxy group content of the polyvinyl acetal resin contained in the first layer, the values of the degree of acetalization, the degree of acetylation, and the hydroxy group content each fall within a region surrounded by a line including four straight lines connecting the first coordinate (degree of acetalization:degree of acetylation:hydroxy group content=70 mol %:30 mol %:0 mol %), the second coordinate (degree of acetalization:degree of acetylation:hydroxy group content=34 mol %:30 mol %:36 mol %), a fifth coordinate (degree of acetalization:degree of acetylation:hydroxy group content=95 mol %:0 mol %:5 mol %), and a sixth coordinate (degree of acetalization:degree of acetylation:hydroxy group content=95 mol %:5 mol %:0 mol %) in the stated order.
 5. The intermediate film for laminated glass according to claim 1, wherein a peak temperature of tan δ which appears at the lowest temperature measured at a frequency of 1 Hz is 0° C. or lower.
 6. The intermediate film for laminated glass according to claim 1, wherein a maximum value of tan δ at a peak temperature of tan δ measured at a frequency of 1 Hz which appears at the lowest temperature is 1.15 or more.
 7. The intermediate film for laminated glass according to claim 1, wherein the second layer contains a polyvinyl acetal resin, and a carbon number of the acetal group of the polyvinyl acetal resin contained in the second layer is 3 or 4, a degree of acetalization thereof is not less than 60 mol % but not more than 75 mol %, and a degree of acetylation thereof is 10 mol % or less.
 8. The intermediate film for laminated glass according to claim 1, wherein the second layer contains a polyvinyl acetal resin and a plasticizer, and the amount of the plasticizer for 100 parts by weight of the polyvinyl acetal resin in the second layer is smaller than the amount of the plasticizer for 100 parts by weight of the polyvinyl acetal resin in the first layer.
 9. The intermediate film for laminated glass according to claim 1, wherein the second layer contains a polyvinyl acetal resin and a plasticizer, and the amount of the plasticizer for 100 parts by weight of the polyvinyl acetal resin in the second layer is not less than 10 parts but not more than 45 parts by weight.
 10. The intermediate film for laminated glass according to claim 1, wherein a ratio of the thickness of the first layer to the thickness of the second layer is not less than 0.2 but not more than
 1. 11. The intermediate film for laminated glass according to claim 1, wherein the second layer is laminated on the first surface of the first layer.
 12. The intermediate film for laminated glass according to claim 1, wherein the second layer contains a polyvinyl acetal resin, the amount of the plasticizer for 100 parts by weight of the polyvinyl acetal resin in the first layer is 50 parts by weight or more, a hydroxy group content of the polyvinyl acetal resin in the first layer is smaller than a hydroxy group content of the polyvinyl acetal resin in the second layer, a difference between the hydroxy group content of the polyvinyl acetal resin in the first layer and the hydroxy group content of the polyvinyl acetal resin in the second layer is 9.2 mol % or less, and a degree of acetylation of the polyvinyl acetal resin in the first layer is 8 mol % or less if a difference between the hydroxy group content of the polyvinyl acetal resin in the first layer and the hydroxy group content of the polyvinyl acetal resin in the second layer is larger than 8.5 mol % but not larger than 9.2 mol %.
 13. The intermediate film for laminated glass according to claim 1, wherein the polyvinyl acetal resin in the first layer contains a high molecular weight component having an absolute molecular weight of one million or more, and a proportion of the high molecular weight component in the polyvinyl acetal resin in the first layer is 7.4% or more; or the polyvinyl acetal resin in the first layer contains a high molecular weight component having a molecular weight in terms of polystyrene of one million or more, and a proportion of the high molecular weight component in the polyvinyl acetal resin in the first layer is 9% or more.
 14. The intermediate film for laminated glass according to claim 1, wherein, in the case that the first layer is used as a resin film and a viscoelasticity of the resin film is measured, a ratio (G′(Tg+80)/G′(Tg+30)) of an elastic modulus G′(Tg+80) at (Tg+80)° C. to an elastic modulus G′(Tg+30) at (Tg+30)° C. is 0.65 or more, provided that Tg (° C.) represents a glass transition temperature of the resin film.
 15. The intermediate film for laminated glass according to claim 1, wherein, in the case that a resin film contains 100 parts by weight of the polyvinyl acetal resin contained in the first layer and 60 parts by weight of triethylene glycol di-2-ethylhexanoate as a plasticizer and a viscoelasticity of the resin film is measured, a ratio (G′(Tg+80)/G′(Tg+30)) of an elastic modulus G′(Tg+80) at (Tg+80)° C. to an elastic modulus G′(Tg+30) at (Tg+30)° C. is 0.65 or more, provided that Tg (° C.) represents a glass transition temperature of the resin film.
 16. The intermediate film for laminated glass according to claim 1, wherein the polyvinyl acetal resin in the first layer is obtained by acetalizing a polyvinyl alcohol resin having an average degree of polymerization of more than
 3000. 17. The intermediate film for laminated glass according to claim 1, further comprising a third layer positioned on a second surface that is an opposite side of the first surface of the first layer.
 18. The intermediate film for laminated glass according to claim 17, wherein the third layer contains a polyvinyl acetal resin, and a carbon number of the acetal group of the polyvinyl acetal resin contained in the third layer is 3 or 4, a degree of acetalization thereof is not less than 60 mol % but not more than 75 mol %, and a degree of acetylation thereof is 10 mol % or less.
 19. The intermediate film for laminated glass according to claim 17, wherein the third layer contains a polyvinyl acetal resin and a plasticizer, and the amount of the plasticizer for 100 parts by weight of the polyvinyl acetal resin in the third layer is smaller than the amount of the plasticizer for 100 parts by weight of the polyvinyl acetal resin in the first layer.
 20. The intermediate film for laminated glass according to claim 17, wherein the third layer contains a polyvinyl acetal resin and a plasticizer, and the amount of the plasticizer for 100 parts by weight of the polyvinyl acetal resin in the third layer is not less than 10 parts but not more than 45 parts by weight.
 21. The intermediate film for laminated glass according to claim 17, wherein a ratio of the thickness of the first layer to the total thickness of the second layer and the third layer is not less than 0.1 but not more than 0.5.
 22. The intermediate film for laminated glass according to claim 17, wherein the third layer is laminated on the second surface of the first layer.
 23. A laminated glass comprising: a first component for laminated glass; a second component for laminated glass; and an intermediate film interposed between the first component for laminated glass and the second component for laminated glass, wherein the intermediate film is the intermediate film for laminated glass according to claim
 1. 